Any Three Doses of mRNA Vaccines Protect You Equally Well Against COVID

Bottom line: It doesn’t matter if you get Pfizer, Moderna or a combo of them—any three doses of these vaccines are the anti-COVID gold standard.

Tara Haelle

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Photo by Braňo on Unsplash

One of the most common questions I still regularly hear from people about COVID-19 vaccines is whether they should get all Pfizer, all Moderna vaccine, or a combination of the two with their booster shots. A new analysis combs through dozens of studies from across the world to provide the best answer to date.

Any three-dose combination of an mRNA vaccine offers the best protection against infection, disease, severe disease, and hospitalization for all known COVID variants, regardless of age and including immune-compromised individuals. According to the new study, published May 31 in BMJ, those who received an adenovirus vector vaccine, such as Johnson & Johnson or AstraZeneca, can increase their protection against disease to nearly 90% with an mRNA booster shot. (See this CDC page’s booster tool to find out whether you need a booster shot and when.)

Starting in March 2022, two researchers from the Chinese University of Hong Kong searched weekly through 38 research databases from the World Health Organization to find studies assessing the effectiveness of different COVID-19 vaccine combinations. They pulled together studies with and without a booster that involved homologous vaccine regimens (all doses of the same vaccine brand) and heterologous regimens (combinations of different vaccine brands). The analysis excluded studies of single shots and only included studies that reported vaccine effectiveness.

Overall, the authors found 53 studies that, together, assessed 24 combinations of different COVID-19 vaccines in just over 100 million people from 15 countries. Eight studies included adults age 65 and older, and seven included children and teens under 18. Another seven studies specifically included high-risk populations — people with at least one chronic condition — and two of these included immune-compromised participants. While most of the studies assessed effectiveness against the initial strain of COVID, 19 of them looked at effectiveness against alpha, beta, gamma, delta, and/or omicron…

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Tara Haelle

Tara Haelle is a science journalist, public speaker, and author of Vaccination Investigation and The Informed Parent. Follow her at @tarahaelle.