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What is known about the safety and efficacy of using different technologies for the first and second doses of COVID vaccines?

This article was published on
June 8, 2021

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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.

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.

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Expert Comments: 

Dave O’Connor, PhD

I'm not sure there are good answers, at least not right now. This new data represents some of the first experimental evidence for ‘real world’ vaccine mixing in a controlled setting. There are lots of anecdotal reports - for example, I received two doses of the AstraZeneca vaccine as part of the US Phase III clinical trial, but nonetheless received a full course of Moderna as the AstraZeneca vaccine has not been approved in the US. And I was pretty reactogenic after the first Moderna vaccine with fever, malaise, and injection site tenderness, none of which I experienced after my AstraZeneca vaccination.

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