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Monday, June 27, 2022

QuickCheck: Is it safe to mix-and-match your Covid-19 booster shot?

A VIRAL video has come out on social media claiming that is unsafe to take an mRDNA vaccine as a booster shot if you were already fully vaccinated with either an adenovirus or viral vector type vaccine. Is this true?



According to a study conducted in Europe, mixing mRDNA vaccines with adenovirus based vaccines can actually produce a more potent immune response.

In April this year, 663 people participated in the Spanish CombivacS trial condcuted by the Carlos III Health Institute in Madrid.

All the participants had already received a first dose of the Oxford–AstraZeneca vaccine (adenovirus).

Researchers randomly picked two-thirds of the participants to receive the mRNA-based vaccine produced by Pfizer and BioNTech eight weeks after their first dose.

The results of the study showed that the Pfizer-BioNTech vaccine seemed to kick-start the immune systems of the participants whose immune systems began to produce much higher levels of antibodies when compared to the control group.

However, another study in the UK, called Com-COV, seemed to show that recipients of mRDNA and edonovirus vaccines did experience higher rates of common vaccine-related side effects, such as fever, than did people who received two doses of the same vaccine.

So while recipients of mix-and-match boosters shots may be more prone to side effects, they will in the long run be better protected against Covid-19.


1. Borobia, A. M. et al. Preprint at SSRN https://ssrn.com/abstract=3854768 (2021).

2. Shaw, R. H. et al. Lancet https://doi.org/10.1016/S0140-6736(21)01115-6 (2021).


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