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What is vaccine-induced thrombosis and thrombocytopenia (VITT)?

Professor Beng Chong an expert on heparin-induced thrombocytopenia (HIT), a condition that closely resembles the blood clot condition linked to the AstraZeneca vaccine. Professor Chong explains what we know about vaccine-induced thrombosis and thrombocytopenia.

What do we know about vaccine passports?

A “vaccine passport” is a proof that someone has been vaccinated against COVID-19. Currently, vaccine passports are being debated in the public health community for their many pros and cons. Vaccine passports are also being used, or planned to be used, in different ways across and within countries globally, which is a trend that is likely to continue.

Why would it have been hard for AstraZeneca to discover blood clots in clinical trials?

The AstraZeneca vaccine went through rigorous Phase 3 testing and regulatory approval processes before being administered in the general public where it has been approved. In the reported Phase 3 trial data of more than 23,000 people, a total of 175 severe adverse events were reported (84 in the study group, 91 in the control group). Three events were considered possibly related to either the control or experimental vaccine. These events included one case of hemolytic anemia (in the phase 1/2 study control group), one case of transverse myelitis (in the study group 14 days after the second vaccine dose), and a case of high fever without another diagnosis (the patient information remains masked as part of the trial). Blood clots were not mentioned in the study published online on December 8, 2020. In clinical trials, it can be very difficult to identify uncommon side effects or serious adverse events (or reactions). When an event is uncommon, it can take a very large study group for it to be observed in research even once. Vaccine studies are designed to evaluate if the vaccine works, and if it is safe. COVID-19 vaccines were studied in clinical trials with thousands of participants before emergency use approval. Even with diverse and large study groups, it is possible that some side effects, reactions, or serious adverse events may not have been seen in the study population. Events that only occur in a few people out of a million or more can be very difficult to detect. In statistics there is a formula that is sometimes used to estimate how many people would need to be studied to detect a serious adverse reaction (SAR). The formula is called the rule of three. For example, if a medication were to cause a SAR in 1 person in every 1,000, then a company would need to study 3,000 people (the rule of 3) in order to have a 95% chance of observing or detecting even one case. For even more rare events that may occur in 1 person in every 10,000, a company would need to study 30,000 people to have a 95% chance of observing or detecting one case. For comparison, the type of rare blood clotting that was observed is estimated to occur in only a few people out of every million.  To help understand more rare adverse effects, drugs and vaccines are studied even after they are approved for the public. Data collection continues for years. This Phase 4 study (or observation) continues as the sample size of the study population is much larger, currently in the many millions for the COVID-19 vaccines. Researchers are continuing to gather data and information about events that occur in people who have received the vaccine. In Epidemiology: An Introduction, a text by Kenneth Rothman, the author notes that a lot of the data around drug safety “comes from studies that are conducted after a drug is marketed.” For the COVID-19 vaccines, government agencies (like the U.S. Food and Drug Administration and others) are collecting data about possible adverse events. Suspected adverse events are reported to the agency, and the agency investigates further. A reported or possible association does not mean that a vaccine caused an event to happen.  Trained researchers monitor and analyze data from these reports. They try to evaluate whether it is likely that the reaction was caused by the vaccine. To do so, they study the possible pathways that could cause the reaction to occur. They also compare the probability of the reaction in those who have been vaccinated to the probability of the reaction in those who have not. Now that many millions of people are being vaccinated with the new COVID-19 vaccines, it is not surprising that some rare events, like allergic reactions and blood clots, are being reported. Researchers now need to work to determine if the events are related to the vaccines and why. Many thousands of blood clots are diagnosed every year. Immobility, surgery, obesity, and smoking are some of the many risk factors. According to the European Medicines Agency, it is possible that blood clots could also be related to receiving the AstraZeneca COVID-19 vaccine. There has not been evidence of issues related to specific batches or a particular manufacturing site for the AstraZeneca vaccine. As of April 4, 2021, a total of 222 cases of thrombosis (169 cases of cerebral venous sinus thrombosis and 53 cases of splanchnic vein thrombosis have been reported) have been reported to EudraVigilance - the European system for managing information about serious adverse reactions to medicines. About 34 million people had been vaccinated in the European Economic Area and United Kingdom by this date.  On April 7, 2021, the European Medicines Agency safety committee concluded “that unusual blood clots with low blood platelets should be listed as very rare side effects of Vaxzevria (formerly COVID-19 Vaccine AstraZeneca).” The U.K. regulatory agency recommended alternatives to the AstraZeneca vaccine to be given to people under 30 years of age, following 79 reported cases of blood clotting and 19 deaths. As of April 16, 2021, the Australian regulatory agency is also conducting a review of the AstraZeneca vaccine following three reported instances of rare clotting, including one fatal case. AstraZeneca has not applied for regulatory approval in the United States, but another viral vector vaccine for COVID-19 made by Johnson & Johnson is also under review for rare blood clotting as of April 13, 2021. Regulatory agencies take vaccine safety seriously and often exercise an abundance of caution. COVID-19 vaccines have been credited with saving lives and reducing hospitalizations on a large scale. 

UK JCVI advice on COVID-19 vaccination for pregnant women

The Joint Committee on Vaccination and Immunisation (JCVI) has advised that pregnant women should be offered the COVID-19 vaccine at the same time as the rest of the population, based on their age and clinical risk group.

Preprint on rare CVT clots after COVID-19 infection vs vaccination

Expert reaction to preprint (not a published paper) looking at incidence of rare cerebral venous thrombosis (CVT) following COVID-19 infection compared to incidence after vaccination or influenza.

What is the risk of CVT following COVID-19, and how it compares to the risk with vaccines

We now know that Cerebral venous thrombosis (CVT) has been reported to occur in about 5 in a million people after first dose of the AZ-Oxford COVID-19 vaccine. But a key question is currently unknown: what is the risk of CVT following a diagnosis of COVID-19? We might expect this to be increased because COVID-19 is associated with other clotting disorders like stroke and brain haemorrhage. New research from the University of Oxford has addressed this question using the TriNetX electronic health records network, recently used to show the neurological and psychiatric consequences of COVID-19 published at the SMC last week. The researchers, led by Professor Paul Harrison and Dr Maxime Taquet from the Department of Psychiatry, counted the number of CVT cases diagnosed in the two weeks after a diagnosis of COVID-19 or after the first dose of vaccine. Please note this data is a preprint, so it is early work that has not yet been through peer-review and is not published in a journal.

NZ's Medsafe seeks more info on Janssen Covid-19 vaccine – Expert Reaction

New Zealand’s medicines regulator has asked for more information from Janssen, with countries putting the company’s Covid-19 vaccine on hold due to rare blood clot concerns. The Janssen vaccine was next in line to be approved for use in New Zealand, but over the past few days the US, EU, and South Africa have all suspended its use. The SMC asked experts to comment.

What do we know about mRNA vaccine side effects?

There is no evidence to suggest that mRNA COVID-19 vaccines or non-mRNA COVID-19 vaccines would result in death, neuro-cognitive issues, debilitating/long-term inflammation, or infertility. 

What do we know about how the Johnson & Johnson vaccine is connected to cases of blood clots?

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.

If someone already got the Johnson & Johnson vaccine, should they be worried? Are there symptoms they should watch for?

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.

Two major adenoviral-vectored vaccines—Johnson & Johnson and AstraZeneca—have been paused because of blood clots. Is there a connection?

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.

How does today’s news on the Johnson & Johnson vaccine from FDA and CDC reflect on the safety of COVID vaccines generally?

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.

How might pausing the Johnson & Johnson vaccine alter vaccine rollout in the U.S?

SciLine reaches out to our network of scientific experts and poses commonly asked questions about newsworthy topics. Reporters can use these responses in news stories, with attribution to the expert.

Coronavirus, Janssen vaccine situation in US and Europe

Expert reaction to Janssen COVID-19 vaccine situation in US and Europe (CDC and FDA recommending a pause in the US while they review six cases of cerebral venous sinus thrombosis (CVST) in combination with low levels of blood platelets (thrombocytopenia); and Johnson & Johnson deciding to proactively delay the rollout of the vaccine in Europe)

Blood clot safety advice changes Aussie COVID-19 vaccine plans

Australia's COVID-19 vaccine rollout has hit a major hurdle with the Government announcing it will accept the advice of the Australian Technical Advisory Group on Immunisation (ATAGI) and prioritise the Pfizer vaccine over the AstraZeneca vaccine for Australians under 50.

Could Covid-19 mutations weaken vaccines? – Expert Q&A

A new Covid-19 mutation nicknamed ‘Eek’, which could reduce vaccine efficacy, is becoming increasingly prevalent. Overseas researchers have said the increase in dominance of variants carrying E484K mutations could seriously complicate vaccination efforts. The SMC posed questions about mutations and vaccines to experts.

Blood clots declared a very rare side effect of AstraZeneca COVID-19 vaccine

The European Medicines Agency has declared a possible link between AstraZeneca's COVID vaccine and rare blood-clotting issues confirming they should be listed as a very rare side effect. There are also reports the Australian Government has asked the national regulator to look into these findings. Below Australian experts comment.

Covid-19 vaccine safety monitoring in NZ – Expert reaction

New Zealand’s medicines regulator has published its first report on adverse reactions experienced by New Zealanders getting the Pfizer Covid-19 jab. There were three serious cases reported out of the more than 15,000 doses given from 20 February to 6 March. Director-General of Health Dr Ashley Bloomfield said this afternoon that all three serious cases were considered allergic reactions and were managed appropriately, and that one of them was classified as an anaphylactic reaction.

MHRA and EMA statements in relation to the AstraZeneca vaccine and rare blood clots and low blood platelets

Medicines regulatory bodies in the UK and Europe, the Medicines and Health products Regulatory Agency (MHRA) and European Medicines Agency (EMA) respectively, have released statements on the Oxford-AstraZeneca COVID-19 vaccine and cases of rare blood clots and low blood platelets.

Ongoing uncertainty around Oxford-AstraZenca COVID-19 vaccine and clotting

Several media reports mention comments made by the European Medicines Agency’s head of vaccine strategy, Marco Cavaleri, who told an Italian newspaper: “In my opinion we can now say it, it is clear that there is an association with the vaccine. However, we still do not know what causes this reaction.”

Valneva reporting phase 1 and 2 data of its COVID-19 vaccine candidate

Valneva have published a press release reporting positive phase 1/2 data for its inactivated, adjuvanted COVID-19 vaccine candidate, VLA2001.

Are COVID-19 vaccines causing new COVID-19 variants?

There is no evidence that vaccines are a source of new COVID-19 variants, or that vaccinated people are more likely to infect others with COVID-19 variants.

MHRA Yellow Card reporting following COVID-19 vaccination, including updated numbers of CVST and other thrombosis events with low platelets

The latest weekly summary of Yellow Card reporting has been published by the Medicines & Healthcare products Regulatory Agency (MHRA), including updated numbers of cerebral venous sinus thrombosis (CVST) and other thrombosis events with low platelets.

Pfizer and BioNTech release on efficacy and safety up to six months after second vaccine dose, including data from South Africa

Pfizer have published a press release stating that updated analysis of their Phase 3 study confirms high efficacy and no serious safety concerns up to 6 months following the second dose of their COVID-19 vaccine.

Welche Therapieoptionen gegen COVID-19 gibt es jetzt?

Die SARS-CoV-2-Variante B.1.1.7 breitet sich in Europa rasant aus und mehrere Länder erleben eine dritte Infektionswelle. Die SARS-CoV-2-Variante B.1.1.7 breitet sich in Europa rasant aus und mehrere Länder erleben eine dritte Infektionswelle.

Results announced by Pfizer-BioNTech on a phase 3 trial of their COVID-19 vaccine in adolescents

Pfizer have published a press release announcing positive topline results of their phase 3 trial of the Pfizer-BioNTech COVID-19 vaccine in adolescents 12 to 15 years of age.

Preprint looking at blood clotting events following vaccination with AstraZeneca’s COVID-19 vaccine

A preprint, an unpublished non-peer reviewed study, posted on Research Square looks at the clinical and laboratory features of 9 patients who exhibited blood clotting events following vaccination with the Oxford-AstraZeneca COVID-19 vaccine.

Parts of Germany suspending the Oxford-AstraZeneca vaccine for under-60s

It has been reported that parts Germany have suspended the use of the Oxford-AstraZeneca in people below the age of 60 amid fresh concerns over blood clotting events.

Preprint looking at immune response after a first dose of the Pfizer vaccine in those with and without prior infection with SARS-CoV-2

A preprint, an unpublished non-peer reviewed study, looks at the T-cell and antibody respondes to the first dose of Pfizer-BioNTech COVID-19 vaccine in previously infected and infection-naïve UK healthcare workers.

AstraZeneca announcing primary data on safety and efficacy from the US trial of the Oxford-AstraZeneca COVID-19 vaccine

AstraZeneca have published a press release stating that the primary analysis of the Phase III trial of the Oxford-AstraZeneca vaccine in the US have confirmed vaccine efficacy consistent with the pre-specified interim analysis announced on Monday 22 March 2021.

Data on the impact of COVID-19 vaccines on mortality in England

Analysis carried out by Public Health England (PHE) suggests that COVID-19 vaccines have prevented thousands of deaths in those aged 70 and older in England in the initial months of the vaccine programme.

What is the COVID-19 arm rash?

The COVID-19 arm rash is a side effect from the vaccine that can cause an itchy or painful rash on the arms of people who have received a vaccine. The rash is harmless and tends to go away within a few days but can be treated with histamine medication or some pain medication if symptoms persist.

AstraZeneca COVID-19 vaccine efficacy questioned

The US National Institute of Allergy and Infectious Diseases (NIAID) has released a statement suggesting AstraZeneca may have included outdated information in the trial of its COVID-19 vaccine, which may have provided an incomplete view of the efficacy data. AstraZeneca has released a response to the NIAID statement here. Below, Australian experts respond to the report.

The use of COVID-19 vaccines in children

A Daily Telegraph exclusive article (https://www.telegraph.co.uk/politics/2021/03/23/exclusive-children-line-covid-vaccines-august/) reported on discussions around children in the UK being offered COVID-19 vaccines in summer. A spokesperson from the Department of Health and Social Care (DHSC) has said: “no decisions have been made on whether children should be offered vaccinations”.

MIQ worker in NZ tests positive after vaccination

A managed isolation and quarantine worker (MIQ) worker in Auckland, New Zealand, has tested positive for Covid-19 after receiving their second vaccine dose.

NIAID statement on the DSMB expressing concern about information released by AstraZeneca on initial data from its COVID-19 vaccine clinical trial in the US

The National Institute of Allergy and Infectious Diseases (NIAID) has released a statement that the Data and Safety Monitoring Board (DSMB) has expressed concern that AstraZeneca may have included outdated information from the US clinical trial of their COVID-19 vaccine, and that this information may have provided an incomplete view of the efficacy data.

What do we know so far about the AstraZeneca vaccine?

The University of Oxford vaccine is being developed and produced by AstraZeneca plc, Inc. and is an adenovirus vaccine (ChAdOx1/AZD1222) currently in Phase 2 and 3 trials in the United Kingdom and India, and in Phase 3 trials in Brazil, South Africa, and the United States. As of December 30, 2020, the vaccine has been authorized for emergency use in adults over 18 years of age in the United Kingdom. Here's a breakdown of everything you need to know so far about this vaccine's development.

What do we know so far about AstraZeneca's vaccine?

AstraZeneca worked in partnership with the University of Oxford to create their vaccine for COVID-19. This vaccine has been approved for emergency use authorization in dozens of countries around the world and uses a formula called a 'viral vector' where a weakened common cold virus (adenovirus) is used to deliver instructions to the body for how to fight COVID-19.

AstraZeneca announcing interim data on safety and efficacy from the US trial of the Oxford-AstraZeneca COVID-19 vaccine

AstraZeneca has published a press release announcing that the Oxford-AstraZeneca COVID-19 vaccine US Phase 3 trial met primary efficacy endpoint in preventing COVID-19 at interim analysis.

UK MHRA statement on the Oxford-AstraZeneca vaccine and blood clots

The UK medicines regulator has released a statement following suspensions of the Oxford-AstraZeneca COVID-19 vaccine by some European countries over suspected blood clots.

Announcement from European Medicines Agency (EMA) on Oxford-AstraZeneca vaccine and blood clots

The European Medicines Agency (EMA) have concluded that the benefits of the Oxford-AstraZeneca COVID-19 vaccine still outweigh the risks despite possible link to rare blood clots with low blood platelets.

What do we know about the AstraZeneca vaccine and blood clotting?

A recent string of blood clotting events in people who had received the AstraZeneca vaccine caused several European nations to halt their use of the shots while they investigated. The European Medicines Agency said that the benefit of the vaccine outweighs the risks and though there have been no direct links between these blood clotting events and the vaccine itself, they will continue to research.

NHS reporting reduced vaccine supply in April

The UK NHS has warned of a significant reduction in COVID-19 vaccine supply in England next month.

Should Australia suspend use of the AstraZeneca COVID vaccine?

Several European countries, including Germany and France, have now suspended use of the Oxford/AstraZeneca (AZ) vaccine after reports of blood clots. Australian senator Matt Canavan has also called on Australia to pause its use of this vaccine. Here, Australian experts comment.

European countries pausing the Oxford-AstraZeneca vaccine over fears of blood clotting

A series of European countries have paused their roll out of the Oxford-AstraZeneca COVID-19 vaccine.

News that Germany has halted vaccinations with the Oxford-AstraZeneca COVID-19 vaccine

It has been reported that Germany have now halted the administration of the Oxford-AstraZeneca COVID-19 vaccine following reports of adverse events related to blood clots in some countries.

European countries put AstraZeneca vaccine on pause

Ireland has joined a growing list of European countries pausing their use of the Oxford/AstraZeneca Covid-19 vaccine after reports of blood clotting. The vaccine manufacturer says its review of the reports show the jab does not increase the risk of blood clotting. New Zealand agreed to purchase enough of the vaccine to immunise 3.8 million people, alongside agreements it made with three other suppliers. New Zealand experts comment on the decisions.

Reports that Ireland has suspended the use of the Oxford-AstraZeneca vaccine

There have been reports that the use of the Oxford-AstraZeneca COVID-19 vaccine has been suspended in the Republic of Ireland following reports of blood clotting events in Norway.

Novavax announcement that their vaccine has high efficacy

Novavax have published a press release stating that their COVID-19 vaccine candidate has shown high levels of efficacy against original and variant COVID-19 strains in United Kingdom and South Africa Trials.

Reported Italy pause of a batch of the Oxford AstraZeneca vaccine as a precaution after two deaths in Sicily

It has been reported that Italy has paused vaccination with the Oxford-AstraZeneca COVID-19 vaccine as a precaution following the deaths of two men in Sicily.

EMA recommending the Janssen COVID-19 vaccine for authorisation in the EU

It has been announced that the European Medicines Agency (EMA) has recommended the single-dose Janssen COVID-19 Vaccine for authorisation in the EU.

Reports that Denmark has paused vaccination with the Oxford AstraZeneca vaccine as a precaution after some reports of blood clots

There have been reports that vaccination with the Oxford-AstraZeneca COVID-19 vaccine is suspended until further notice in Denmark after reports of cases of blood clots.

Preprint looking at antibody immune response following one dose of Pfizer COVID-19 vaccine in cancer patients

A preprint, an unpublished non-peer reviewed study, looks at the safety and immune-efficacy of 1 versus 2 doses of the Pfizer-BioNTech COVID-19 vaccine in cancer patients.

Commentary on vaccination priorities and ethnicity

A commentary piece published in the Journal of the Royal Society of Medicine addresses the UK’s colour-blind strategy to COVID-19 vaccine allocation.

What do we know about the risks of combining more than one of the approved vaccines?

For COVID-19 vaccines that require more than one dose, such as the Pfizer-BioNTech and Moderna vaccines, researchers are still learning about the outcomes of mixing a first dose of one vaccine with a second dose of another. In the clinical trials that have led to emergency authorization of COVID-19 vaccines, combining doses from different vaccines has not yet been tested. This means that scientists do not yet know if combining doses from different COVID-19 vaccine candidates will be as effective or safe. To help provide more data, a clinical trial was announced on February 8, 2021 to begin testing the combination of one dose from the AstraZeneca vaccine candidate with one dose from the Pfizer-BioNTech vaccine candidate. This clinical trial, dubbed Com-Cov, is being led by the University of Oxford and is considered the first in the world to test the combination of different COVID-19 vaccine candidates. Enrollment of 820 participants over 50 years of age is starting, and scientists hope this clinical trial can provide more data and insights by the summer of 2021. It is important to remember that outcomes can potentially vary depending on which COVID-19 vaccines are mixed. For this reason, the first clinical trial testing a combination of the AstraZeneca and Pfizer-BioNTech vaccine candidates may eventually add additional vaccine candidates. As more COVID-19 vaccine candidates become ready for approval, more studies may be needed to understand the outcomes of combining doses between the multiple available vaccine candidates. There are many potential benefits to being able to combine COVID-19 vaccine candidates, which is why scientists are eager for more data to evaluate this. Ramping up COVID-19 vaccine supplies and coordinating distribution remain a challenge, so being able to give vaccines based on availability could mean more people receive the vaccinations faster and more lives are saved. The U.K.'s deputy chief medical officer has said that there may be benefits to having data that could support more "flexible" vaccination programs, since there is currently an insufficient global supply of COVID-19 vaccines. Beyond the logistical benefits, there could potentially be immunological benefits of using two different vaccines to combat the same pathogen in certain cases. For COVID-19 vaccines that are given in two doses, the "prime" dose is followed by a "boost" dose to help stimulate and amplify the body's immune response, with the goal of developing immunological memory to protect against COVID-19 infections in the future. The strategy of using doses from different vaccines is known as "heterologous prime-boost." Some COVID-19 vaccine candidates, like the Russian Sputnik V, have even been designed to use this strategy with the first and second doses containing different viral components. With newer and faster-spreading variants of COVID-19 emerging around the world, some of which could be partially resistant to immune responses triggered by the vaccines, scientists are also planning to investigate whether combining different vaccines can help offer more protection. Multiple COVID-19 vaccine candidates have been developed in record speed to help combat the global pandemic. In order to take full advantage of every tool that is available for pandemic response, scientists are studying the potential of combining doses from different COVID-19 vaccine candidates. As more data becomes available, public health experts and policymakers will be able to make more informed decisions about "mixing and matching" COVID-19 vaccine doses.

Priority groups for Covid-19 vaccination in New Zealand

Those at high risk of Covid-19 in south Auckland and certain aged care facilities will be priorities for the vaccine roll-out after border and frontline healthcare workers. Following this group will be over-65s and people with underlying health conditions across the country. The vaccine will then be distributed to the remainder of the population. The SMC asked experts to comment on the roll-out plan.

NEJM correspondence paper looking at the neutralising activity of the Pfizer-BioNTech vaccine against SARS-CoV-2 variants in the lab

A correspondence paper, published in the New England Journal of Medicine (NEJM), looks at the neutralising activity of Pfizer-BioNTech COVID-19 vaccine-elicited serum against different SARS-CoV-2 variants.

Aviation worker tests positive for Covid-19 shortly after vaccination

An Air New Zealand flight attendant tested positive for Covid-19 on Sunday, shortly after receiving a shot of the Pfizer vaccine. Prime Minister Jacinda Ardern said on Monday morning the vaccine takes a couple of weeks to work, so they wouldn’t have expected the person to be protected from the virus. The SMC asked experts to comment.

Vaccine Basics

Vaccines have delivered enormous public health benefits including the global eradication of smallpox, the near eradication of polio, and greatly reduced incidence of measles, meningitis, and other serious and potentially fatal diseases. Even before the approval of vaccines to protect against COVID-19, which in its first year killed about 2.5 million people worldwide, vaccines were regularly preventing two million to three million deaths per year. A large body of rigorous science has clearly and repeatedly shown that vaccines in use today—which rely on several different strategies to impart immunity—are exceedingly safe, with benefits greatly outweighing risks for individuals in groups recommended to get them.

Vaccine Successes and Current Uses

A large body of rigorous science has clearly and repeatedly shown that vaccines in use today are exceedingly safe, with benefits greatly outweighing risks for individuals in groups recommended to get them. Contrary to widely disseminated misinformation about the purported dangers of vaccines, serious adverse health effects are very rare, while public health benefits are vast.

Vaccine Testing

A large body of rigorous science has clearly and repeatedly shown that vaccines in use today are exceedingly safe, with benefits greatly outweighing risks for individuals in groups recommended to get them. Contrary to widely disseminated misinformation about the purported dangers of vaccines, serious adverse health effects are very rare, while public health benefits are vast.

Vaccine Safety

A large body of rigorous science has clearly and repeatedly shown that vaccines in use today are exceedingly safe, with benefits greatly outweighing risks for individuals in groups recommended to get them. Contrary to widely disseminated misinformation about the purported dangers of vaccines, serious adverse health effects are very rare, while public health benefits are vast.

Preprint assessing the effectiveness of the first dose of Pfizer-BioNTech and Oxford-AstraZeneca COVID-19 vaccines in prevention of hospitalisations in elderly and frail adults

A preprint, an unpublished non-peer reviewed study, assesses the effectiveness of one dose of the Pfizer-BioNTech and Oxford-AstraZeneca COVID-19 vaccines against hospitalisations in the over 80s.

Preprint looking at the early effectiveness of COVID-19 vaccination with the Oxford-AstraZeneca or Pfizer-BioNTech vaccine on symptomatic disease, hospitalisations and mortality in older adults in the UK

A preprint, an unpublished non-peer reviewed study, suggests both the Pfizer-BioNTech and Oxford-AstraZeneca vaccines reduce severe COVID-19 in older adults.

Preprint on asymptomatic infections after a single dose of the Pfizer-BioNTech vaccine

A preprint, an unpublished non-peer reviewed study, suggests that a single dose of the Pfizer-BioNTech COVID-19 vaccine reduces asymptomatic infections.

What are human challenge trials for vaccines?

A human challenge trial (HCT) is a study that deliberately infects volunteers with a virus after they've been given a vaccine, in order to see if the vaccine is effective. Clinical trials usually allow participants to be exposed to COVID-19 in their day-to-day lives, but HCTs intentionally infect volunteers in order to learn about the virus, immune responses, medications, and treatments.

Vaccine program kicks off in Australia

Australia's vaccine program kicks off in earnest today with a phased program that begins with the Pfizer-BioNTech vaccine for the most vulnerable people in the community. Australian experts respond.

Rolling out the Covid-19 vaccine in New Zealand

Vaccinators are the first people in New Zealand to get the Pfizer/BioNTech Covid-19 jab. Border and MIQ workers and their families will start getting vaccinations next, with the government planning to immunise thousands by mid-March as part of its rollout plan. The SMC asked experts to comment on the rollout.

Emerging COVID-19 Challenges: Long-COVID and Viral Variants

A year into the global COVID-19 pandemic, physicians and researchers are battling two newly frustrating phenomena: the spread of novel coronavirus variants with potential to undermine patients’ immune-system defenses, and a mysterious long-lasting medical syndrome in survivors, for which there remains no definitive treatment. SciLine’s media briefing dove into the latest research on these biomedical challenges, and provided reporters with opportunities for Q&A.

What do we know so far about the COVID-19 vaccines during or before pregnancy and breastfeeding?

None of the three leading vaccine manufacturers (Pfizer, Moderna, and AstraZeneca) have reported data about the COVID-19 vaccine on knowingly pregnant or breastfeeding individuals. As a result, we have a limited understanding of how effective the three leading vaccines are for pregnant and breastfeeding people, and if there are specific risks.  Given this lack of data, some regulators and public health entities have not included pregnant people in their vaccine recommendations to the public with some specifically warning pregnant individuals against taking the vaccine. The WHO was one of these entities until Friday, January 29. Previously their guidance said that the vaccine was "currently not recommended" for pregnant women unless they are at high risk of exposure.  While their guidance, in practice, is still similar, recommending pregnant people with comorbidities or at high risk of exposure may be vaccinated in consult with doctors, they’ve directly noted that we “don’t have any specific reason to believe there will be specific risks that would outweigh the benefits of vaccination for pregnant women.” Until there is more data on COVID-19 vaccines and pregnancy, this trend of mixed guidance across different regulatory bodies and countries is likely to if and as vaccines continue to get approved.  Pregnant people who do receive a vaccine may be able to produce an immunity to the virus from the vaccine that can cross the placenta which would help keep the baby protected after birth. Regarding safety, however, when you receive an mRNA vaccine for COVID-19 you expel the mRNA particles from your body within days, so if pregnant it’s unlikely to cross the placenta and impact the baby. The process for collecting this data will involve analyzing the impacts of the vaccines on individuals who receive a vaccination and later discover that they’re pregnant. Countries are coordinating internal reporting and monitoring systems to record and track this information.  The clinical trials had some participants enrolled who didn’t know they were pregnant at the time of vaccination, but there were not enough of those cases to have enough data for definitive conclusions. For example, in Phase 2/3 of the Pfizer and BioNTech vaccine study, 23 pregnancies were reported through November 14, 2020. Twelve were in the vaccine group and 11 in the placebo group. Two adverse events occurred in pregnancies in the placebo group, including miscarriage. These initial data do not raise concern for lack of vaccine safety in pregnancy and breastfeeding, but more data is needed to safely recommend the use of this vaccine by pregnant and breastfeeding individuals. The U.S. FDA also recommended in June 2020 that the pharmaceutical companies developing COVID-19 vaccines first conduct developmental and reproductive toxicity (DART) studies of their vaccine before enrolling pregnant or breastfeeding people, or women not actively avoiding pregnancy, in their trials.  Pfizer and BioNTech have directly stated that they are conducting DART studies, which will provide us with more information on the safety and efficacy of their vaccine for pregnant and breastfeeding individuals. On December 13, the American College of Obstetricians and Gynecologists released a position paper advocating for the inclusion of pregnant women in vaccine rollouts and not waiting for further data collection. While the group advocates for obtaining informed consent from pregnant and lactating women receiving the vaccine, they feel the benefits of protection outweigh the risks. The U.S. Centers for Disease Control and Prevention (CDC), the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine support the use of new mRNA COVID-19 vaccines in pregnant and breastfeeding individuals when they become eligible for receiving the vaccine. As of January 26, 2021, the World Health Organization also supports pregnant and breastfeeding women receiving the Moderna mRNA vaccine if they choose. Before more data is available, it is best for pregnant and breastfeeding individuals to speak with their doctors about the best way to proceed. While it is unlikely that a doctor would recommend a pregnant or breastfeeding person get vaccinated before more data is available unless they were high risk, every risk profile is different and is worth discussing with a care provider.

Made in Australia - COVID-19 vaccine manufacturing explained

As the Australian Government prepares to roll out the COVID-19 vaccination program, CSL has been busily manufacturing the AstraZeneca COVID-19 vaccine (recombinant adenovirus vaccine). CSL has a contract to manufacture 50 million doses of the AstraZeneca vaccine for use by Australians and is on track to deliver the first doses - tested, approved and released by the TGA (subject to TGA approval) – from late March. Representatives from CSL and Seqirus’ advanced manufacturing facilities in Broadmeadows and Parkville, Victoria will explain the process of manufacturing the AstraZeneca vaccine – starting from the first ‘vial thaw’ through to ‘harvest’ of the product in bulk, to formulation and ‘fill and finish’ into dose vials.

WHO Interim report recommends AstraZeneca vaccine

The WHO has released interim recommendations for the use of the Oxford/AstraZeneca vaccine, recommending its use for healthcare workers and elderly people as a priority to reduce COVID deaths and transmission. Here's what the Aussie experts have to say.

How COVID vaccines are handling the new variants

A new report have been released about the efficacy of the Pfizer-BioNTech vaccine against the new variants of COVID-19. A paper released by Nature Medicine suggests the Pfizer-BioNTech COVID-19 vaccine (BNT162b2) is shown to neutralize the United Kingdom and South African variants of SARS-CoV-2 (N501Y and E484K mutations). Here's what Australian experts have to say...

News reports that the Oxford/AZ vaccine gives limited protection against mild disease caused by the South African variant of SARS-CoV-2

There have been news reports that the Oxford/AstraZeneca COVID-19 vaccine provides limited protection against mild disease caused by the SARS-CoV-2 variant first detected in South Africa, 501Y.V2.

Preprint from Oxford looking at efficacy of the Oxford AstraZeneca vaccine against the B.1.1.7 ‘Kent’ UK variant of SARS-CoV-2

A preprint, an unpublished non-peer reviewed study, looks at efficacy of the Oxford/AstraZeneca vaccine against the ‘Kent’ variant of SARS-CoV-2, B.1.1.7.

Why are there multiple COVID-19 vaccines?

Dozens of countries have now rolled out mass vaccination campaigns using a variety of vaccines. Knowing this, it makes sense to question why more than one or two or these vaccine formulas are necessary. The answer to this is as multi-faceted as populations are diverse, but in short, we will need multiple vaccines to stop the pandemic. No one pharmaceutical or biotechnology company would be able to produce enough product and distribute it to the entire global population fast enough to curb the pandemic. Producing more than one vaccine also means that manufacturing delays become less risky. With the world relying on multiple companies to produce the live-saving products, delivery delays of one vaccine can be offset by the production of other vaccines. For countries with electricity challenges, last mile health outposts, and a lack of roads, it is not always feasible to deliver Pfizer and Moderna's mRNA vaccines, because of the refrigerated temperatures they require for transport. Many countries will likely rely on another vaccine formulation that has a longer shelf life and has no refrigeration requirements. Cost is another reason for multiple vaccines. High resource-countries have pre-purchased millions of different vaccines directly from distributors in order to immunize their populations, which is not possible for some countries. Vaccine prices range from a couple of US dollars per dose to roughly $50, depending on the producer. Many countries do not have the financial resources to spend billions of dollars in addition to their annual health budgets to procure vaccines for their populations. As such, dozens of countries are reliant on programs like COVAX to help them obtain free or low-cost vaccines for their citizens. Lastly, vaccines need to protect diverse groups of people. Every person will respond differently to each vaccine and have a different immune response. So having a variety of vaccine types fill these needs is a more concrete strategy than relying on or or two vaccines alone. We still have many unanswered questions about how long immunity might last, who might have a more robust immune system response than others, or even how effective they might be in children.

Where can I find information on adverse reactions from the vaccines? How are they being reported and made public?

Most regulatory policies require COVID-19 vaccine candidates to go through rigorous clinical trials, which include documentation of adverse reactions. The vast majority of participants in COVID-19 vaccine clinical trials did not experience severe adverse reactions. Results from the clinical studies are published and publicly available. One platform that consolidates the results is the COVID-19 Real-Time Learning Network, which is made available thanks to a collaboration between the U.S. Centers for Disease Control and Prevention (CDC) and the Infectious Diseases Society of America (IDSA). Additionally, now that COVID-19 vaccine candidates have been given to millions of people around the world, more data is becoming available from countries that are monitoring the vaccine distribution and collecting information. For example, in the United States, adverse reactions can be reported by providers of the COVID-19 vaccines, as well as by recipients on the national VAERS (Vaccine Adverse Event Reporting System) online platform. This reporting system is part of the many expanded vaccine safety monitoring systems that have been developed. Based on early data from these reporting systems, the U.S. CDC released a report in January 2021 on anaphylaxis, a severe and potentially life-threatening allergic reaction that rarely occurs after vaccination. This report is publicly available, along with several other reports and resources, and includes recommendations such as ensuring that patients with previous history of similar allergic reactions are monitored for 15-30 minutes following COVID-19 vaccination and are taught how to recognize signs of anaphylaxis. If someone has questions about potential adverse reactions because of their health status, including any pre-existing health conditions, please consult with a healthcare provider. If someone has received a COVID-19 vaccine dose and has experienced serious adverse side effects, please consult with a healthcare provider and report the adverse effects to a vaccine safety monitoring system as appropriate. For reference, the U.S. CDC has provided a list of what is normal to expect after COVID-19 vaccination, including typical minor side effects: <https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html>

How are manufacturers making adjustments to COVID-19 vaccines?

Pfizer-BioNTEch and Moderna have started working on booster doses for their vaccines because of concerns that current versions will be less effective against new, possibly more contagious, COVID-19 variants.  Pfizer-BioNTEch and Moderna vaccines are made using mRNA, which is like a genetic software code that can be updated relatively easily and quickly. Tweaking the vaccine can be done in a couple of days, but updated vaccine trials might require more time. The FDA's testing process and policy for the new booster shots is not yet known, but is expected to be publicized soon. Some experts suggest that the end result may look similar to the FDA's process for the flu vaccine, which changes every year but does not go through full-scale clinical trial phases every time an adjustment is made. Viral mutations are a common phenomenon in infectious diseases. COVID-19 vaccine manufacturers report that their vaccines work against the mutations identified in the U.K. and South Africa, but their laboratory studies suggest that the vaccines are less effective against the variant identified in South Africa.

How are vaccines studied for long-term side effects?

After vaccines are approved for use they are monitored closely by national and international health and medicine regulators. Studying long-term effects of vaccines helps health authorities ensure that protection from taking a vaccine outweighs risks. The United States uses several reporting mechanisms for monitoring long-term vaccine side effects. They include: - Vaccine Adverse Event Reporting System (VAERS) which works as an early warning system to detect possible safety issues with vaccines by collecting information about possible side effects or health problems that occur after vaccination - The Vaccine Safety Datalink (VSD) which helps discover if possible side effects identified using VAERS are actually related to vaccination - The Post-Licensure Rapid Immunization Safety Monitoring (PRISM) system which is the largest vaccine safety surveillance system in the United States and actively monitors a subset of the general population for vaccine impacts - The Clinical Immunization Safety Assessment (CISA) Project which works alongside health systems to consistently monitor and evaluate the safety of vaccines throughout large populations Additionally, the U.S. CDC unveiled V-safe in response to COVID-19. V-safe is a smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after you receive a COVID-19 vaccine. Using V-safe allows vaccine recipients to quickly tell the CDC if they are experiencing any side effects after getting the COVID-19 vaccine. Depending on which side effects people are experience, someone from the CDC may call to check on them and get more information.  Monitoring vaccines and reporting any side effects to local and national health agencies is an important part of the vaccine process. Any reports of a potential side effect from a vaccine can lead to health officials issuing new recommendations or warnings, restricting the vaccine, or even recalling it if necessary (but very few vaccines have even been recalled). Though safety and efficacy data are intensely reviewed before vaccines are approved for usage, constant monitoring of their side effects is a necessary step in ensuring the public's safety.

If vaccines come on the market that are less effective than existing vaccines against new variants of SARS-COV-2, should people get them or wait until more effective vaccines are available?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

How challenging is it to update different types of vaccines?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

How will scientists decide when to update vaccines in response to new SARS-CoV-2 variants?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

Medsafe approves NZ’s first Covid vaccine

The Pfizer/BioNTech vaccine (Comirnaty) has been provisionally approved for use by New Zealand’s medicines regulator. Medsafe has placed 58 conditions on the approval, most of which relate to seeing more data as the company scales up its manufacturing.

Russian trial suggests SPUTNIK V vaccine shows 91.6% efficacy

It has been reported in The Lancet that a Russian trial of the Sputnik V vaccine in 20,000 people found it has an efficacy of 91.6 per cent, and does not cause any serious adverse events. An Australian expert responds to the results.

Novavax vaccine shows 89.3% efficacy in phase 3 trial

It has been reported that the Novavax COVID-19 Vaccine has demonstrated an 89.3% efficacy in its UK phase 3 trial. Experts comment on the findings.

AstraZeneca COVID-19 vaccine in older adults

Uncertainty about the efficacy of AstraZeneca's COVID-19 vaccine in people over 65 years has caused some confusion in media reports, with some saying it may be much less effective in older people. AstraZeneca have stated that this claim is incorrect and scientists have pointed out that the numbers of older people tested with the vaccine is very low (ie. absence of evidence is not evidence of absence). Australian experts comment.

How do mRNA messenger vaccines work?

A vaccine’s role is to teach the immune system how to recognize a foreign body (the coronavirus in this case) that could make a person sick. Once the immune system is able to identify a harmful invader, it can attack the actual virus if it enters the body. Most vaccines are made from an inactivated or weakened pathogen (bacteria or virus). Because the virus in the vaccine is weakened or inactivated, they don’t cause severe disease in the body but are able to train the immune system to recognize the invader and be able to fight it by creating antibodies. These antibodies are a special kind of protein that know how to fight that specific virus. The immune system then remembers to make these antibodies in case such virus does enter our body in the future, and thus prevent disease. mRNA vaccines or "messenger RNA" vaccines are different. They're a type of vaccine that does not carry an inactivated or weakened pathogen. Instead, they carry information, which instructs the cells in the body to create a protein or a part of a protein, which in turn triggers an immune response. Teaching the cells to create this harmless but foreign protein allows the body to activate its immune system. On seeing a foreign element in the system, the immune system fires into action and starts producing antibodies to fight against the invader. Soon after making the protein, our cells break down the mRNA and get rid of it. mRNA COVID-19 vaccines cannot cause COVID-19 because they do not carry the full information needed to make the SARS-CoV-2 virus in the body. They only carry information from a specific protein found on the surface of the SARS-CoV-2 virus. mRNA vaccines are faster to produce (about a week) as compared to conventional vaccines that can take many months to produce an experimental batch. The production of mRNA vaccines is safer than traditional vaccine production as it doesn’t require actual viruses, whereas, producing traditional vaccines require growing large quantities of actual virus and can pose to be a potential biohazard. Although traditional vaccines are very effective, it has been posited that mRNA vaccines could create an even stronger immune response to certain viruses, but more evidence will need to be gathered on that. One challenge of mRNA vaccines is that it is very fragile and needs to be stored at very cold temperatures.

Could mRNA vaccines create a different protein than expected that could result in autoimmune disease down the road?

COVID-19 mRNA vaccines help our bodies create spike proteins, which generate an immune response to fight the COVID-19. There is no evidence that mRNA vaccines create other proteins, and there is no evidence that mRNA vaccines cause autoimmune diseases. 

Answering your questions about COVID-19 variants

With reports of new COVID-19 strains emerging in the UK, South Africa, and Brazil, an Australian expert answers key questions about the new strains and how they might impact the current COVID-19 vaccines.

If new—or future—variants of SARS-CoV-2 evade currently approved vaccines, are there vaccines in development that might prove more effective or that target a different part of the virus?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

Why might several different variants of SARS-CoV-2 have appeared recently?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

How do mutations in these variants change the virus's ability to infect people?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them

What new variants of SARS-CoV-2 are concerning?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

Should someone still get the first dose of a COVID-19 vaccine, without assurance that a second dose will be available?

For COVID-19 vaccines that are designed to have two doses, it is important to get both doses to maximize protection. In late 2020, the U.S. Food and Drug Administration (FDA) authorized emergency use of COVID-19 vaccines from Moderna and Pfizer / BioNTech, both of which are designed to be implemented in two-doses.  Studies have shown each of these vaccine candidates to be relatively safe and ~95% effective at preventing symptomatic COVID-19 disease in adults after both doses. There are many reasons why a second dose may become delayed or unavailable due to issues like limited vaccine supply and other logistical challenges. As a result, there are proposals to ration vaccine doses or to initially give a single dose to as many people as possible. The reaction of scientists to these proposals is mixed, because of limited data on the impacts of changing recommended vaccine dosing. According to data provided by Moderna, one exploratory analysis of participants who received just one dose of its vaccine suggested that the efficacy in protecting against symptomatic COVID-19 could be around 73%, in the short-term. Efficacy in protecting against symptomatic COVID-19 after the first dose of the Pfizer vaccine was about 52.4%, with most of the cases happening in the days immediately following the first dose. From day 10 after the first dose until the second dose, the efficacy in protecting against symptomatic COVID-19 was around 89%.  It is important to note that the second dose was given on day 21 in these Pfizer / BioNTech trials, so there is limited data on how well the first dose would protect someone after day 21.   On January 4, 2021, the FDA issued a statement about following the authorized vaccine dosing schedules, saying: “We have been following the discussions and news reports about reducing the number of doses, extending the length of time between doses, changing the dose (half-dose), or mixing and matching vaccines in order to immunize more people against COVID-19. These are all reasonable questions to consider and evaluate in clinical trials. However, at this time, suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence.” More research is being done to help answer the question about how beneficial it is to change a recommended vaccine dosing schedule in order to stretch limited supplies to as many people as possible. 

What are potential benefits and drawbacks of administering a second vaccine dose from a different brand than the first?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

What data would be necessary to determine whether delaying or even eliminating a second dose to give more people first doses would be a net benefit?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

Why are the currently approved COVID-19 vaccines administered as two separate doses?

SciLine tracks common science questions that reporters have about the coronavirus pandemic – and reaches out to our network of scientific experts for quotable comments in response. Reporters can use the comments below in news stories, with attribution to the scientist who made them.

Is it safe or effective to get a vaccine dose for COVID-19 while testing positive?

The U.S. Centers for Disease Control and Prevention (CDC) does recommend that people who have had COVID-19 still get vaccinated, because it may be possible to get reinfected and vaccines can sometimes induce better immunity than natural infection. However, this recommendation typically applies to people who have recovered from COVID-19, rather than people who are currently still sick. For people who currently have an active COVID-19 infection, their bodies are already creating antibodies in response, so health experts recommend waiting until after recovery for vaccination. Researchers are still understanding how immunity evolves over time, but it is generally thought that most people have some level of protection against reinfection for the first few months after recovery. The U.S. CDC even suggests that people who have not had COVID-19 in the past 90 days should be a higher priority for vaccination than people who have had COVID-19 recently. Additionally, it takes time for the body to develop immunological protection after vaccination, and vaccines requiring two doses do not have maximum protection until after the second dose. This means that it is still possible for someone to become sick if exposed to COVID-19 before or immediately after vaccination. People who are known to have COVID-19 may not be able to go receive vaccinations until after they recover because they could risk getting others sick. Scientists are continuing to learn about the safety and efficacy of COVID-19 vaccines with the ongoing studies and data collection. For vaccines that have been approved by regulatory agencies and are already in the market, phase 4 clinical trials (also called “open-label studies” or “post-marketing surveillance”) are a way to continue studying the risks and potential benefits over a longer period of time. More data will become available in the future. 

Why is Janssen starting a clinical trial with two doses?

Janssen Pharmaceuticals, part of Johnson & Johnson, has designed a COVID-19 vaccine candidate to be delivered in a one-dose regimen. The company is also starting a clinical trial for a two-dose regimen. Johnson & Johnson announced that the new phase 3 trial for a two-dose regimen has been planned to be complementary and run in parallel with the ongoing phase 3 trial for a one-dose regimen, erring on the side of caution in case two doses have the "potential to offer enhanced durability in some participants." The existing phase 3 trial for a one-dose regimen, called ENSEMBLE, has been enrolling participants with a goal of testing the Janssen vaccine candidate with up to 60,000 people from multiple countries around the world. The newer phase 3 trial for a two-dose regimen, called ENSEMBLE 2, intends to test two doses of the Janssen vaccine candidate with up to 30,000 participants from multiple countries around the world. These ENSEMBLE and ENSEMBLE 2 trials follow the promising interim results from the phase 1/2a clinical trial of the Janssen vaccine candidate, which has been studying both one-dose and two-dose regimens for preliminary data on safety and effectiveness. Due to the urgent nature of the COVID-19 global pandemic, many phases of vaccine development and testing have been implemented in parallel. For example, sometimes clinical trial phases are combined into a phase 1/2 or 2/3 trial, or a later phase trial is started in parallel based on promising interim results of an earlier phase trial (rather than doing trials sequentially that wait for an earlier phase trial to be completed before starting a later phase trial). Johnson & Johnson is not the only major vaccine developer to be running clinical trials in parallel. Scientists will be able to say more about the effectiveness of the one-dose and two dose regimens after more data from the parallel phase 3 trials become available.

What do we know about how an mRNA vaccine interacts with human cells?

The human body has lots of different types of cells, and they serve many different purposes. MRNA vaccines like Pfizer and Moderna's vaccines interact with multiple types of cells once they enter the human body, including immune cells, which are the cells that launch a response to the virus and help us build immunity to COVID-19. Additionally, "T-follicular helper cells" (T cells) are a type of immune cell that is activated by the mRNA vaccine. "Germinal center B cell responses" (GC B cells) are also activated by the mRNA vaccine.  mRNA vaccines also interact with dendritic cells. Dendritic cells help our bodies with transporting foreign invaders, like a virus or a vaccine, to the body's immune-boosting T cells, so that we can build up immunity to that foreign invader. Lastly, the mRNA vaccines also interact with cells in our muscles when the vaccine is injected.

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About the Hub

The COVID-19 Vaccine Media Hub is a dedicated resource for journalists and fact checkers wanting access to evidence-based information on COVID-19 vaccines. The Hub brings together multiple sources of evidence-based information on vaccines, including explainers, expert commentary, the latest research and online press briefings, with material soon to be available in multiple languages.

If you’re a fact checker or a journalist, we’re here to help you find the information and experts you need for your story.

If you’re a member of the public and would like help finding information on COVID-19 vaccines, feel free to browse the site. You might also like to explore other evidence- based vaccine information sites such as the WHO's COVID-19 vaccine page.

This project is a global effort with contributions from Science Media Centres in Australia, the UK, Germany and New Zealand plus technology not-for-profit, Meedan. Other contributors are based in North America, Africa, Latin America and the Asia Pacific region.

The COVID-19 Vaccine Media Hub is supported by the Google News Initiative.

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The Australian Science Media Centre works to enhance the media’s coverage of science, for the benefit of the public. We provide the evidence and experts when science hits the headlines.

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SMC Taiwan was established in 2017, as one of the international SMCs. SMC Taiwan is the only SMC in Asia connecting journalists and scientists to provide evidence-based information through the media. Please contact us if you require any assistance with reporting COVID-19. 關於疫情若需要任何進一步的專家意見,以協助民眾判讀各式科學資訊,都歡迎隨時聯繫我們。 SMC Taiwan是國際科學媒體中心的一員,唯一的亞洲科學家媒體媒合平台,會持續提供專家意見與相關研究討論,給各位媒體朋友們參考。