Mix-and-match vaccines? Scientists say changing brands for your COVID booster provides more protection

LISBON, Portugal – What is the best COVID booster strategy? New research shows evidence that mixing and matching COVID-19 vaccines provides more protection against the virus than getting three doses of the same brand.

The study looked at the vaccine effectiveness of CoronaVac, the Oxford-AstraZeneca vaccine, and the Pfizer-BioNTech booster shot in individuals who previously had two doses of the CoronaVac vaccine in Chile. The two-dose CoronaVac vaccine makes up more than half of COVID-19 vaccine doses globally.

Study participants received their vaccines between Feb. 2 and Nov. 10, 2021. They excluded individuals with a prior SARS-CoV-2 infection before Feb. 2 and those who received at least one COVID-19 vaccine dose before that date.

A total of 4,127,546 people had two doses of the CoronaVac vaccines and later received a booster dose. Results show 46.5 percent of participants received the Oxford-AstraZeneca booster shot, 48.9 percent received a Pfizer-BioNTech booster, and 4.5 percent received a third dose of CoronaVac.

Keeping it the same is a bad strategy

The study finds receiving a CoronaVac booster elicited a 79-percent vaccine effectiveness against symptomatic COVID-19 infection. It also produced an 86-percent protection rate against COVID-related hospitalizations, a 92-percent protection rate against ICU admission, and an 87-percent protection rate against death.

In comparison, researchers found that patients had a 97-percent vaccine effectiveness after receiving the Pfizer-BioNTech booster. They also had 96 percent protection against hospitalization and ICU admission. Getting the Pfizer-BioNTech booster also led to a 97-percent rate of protection against COVID-related death.

For people receiving the AstraZeneca booster, their vaccine effectiveness was 93 percent. It also provided 98 percent protection from both hospitalization and death and 99 percent protection from ICU admission.

The findings suggest that getting any kind of third booster shot better protects you against hospitalization and death during the pandemic. However, getting a different vaccine from your primary immunization increases your protection level.

“Our results suggest that a third dose of CoronaVac or using a different booster vaccine such as Pfizer-BioNTech or Astra Zeneca vaccines in those that had previously had two doses of CoronaVac provides a high level of protection against COVID-19, including severe disease and death…However, receiving a different vaccine for the booster dose results in higher vaccine effectiveness than a third dose of CoronaVac for all outcomes, providing additional support for a mix-and-match approach,” the researchers from Chile write in a media release.

The team presented their findings, published in The Lancet Global Health, at the European Congress of Clinical Microbiology & Infectious Diseases.

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About the Author

Jocelyn Solis-Moreira

Jocelyn is a New York-based science journalist whose work has appeared in Discover Magazine, Health, and Live Science, among other publications. She holds a Master’s of Science in Psychology with a concentration in behavioral neuroscience and a Bachelor’s of Science in integrative neuroscience from Binghamton University. Jocelyn has reported on several medical and science topics ranging from coronavirus news to the latest findings in women’s health.

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