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A booster shot of mRNA or viral vector SARS-CoV-2 vaccine after 2 doses of an inactivated virus vaccine better protected patients against severe disease and death from COVID-19 than 3 doses of the inactivated virus vaccine, according to a large-scale study in The Lancet Global Health. The findings give additional support for a mix-and-match approach to COVID-19 boosters, the authors wrote.
The observational study involved about 4.1 million patients in Chile who received 2 doses of the CoronaVac (Sinovac Biotech) inactivated virus SARS-CoV-2 vaccine. Among them, 4.5% also received a CoronaVac booster while 48.9% received a BNT162b2 (Pfizer-BioNTech) mRNA vaccine booster and 46.5% received an AZD1222 (Oxford-AstraZeneca) viral vector vaccine booster.
Compared with unvaccinated patients, the homologous booster with the CoronaVac vaccine was 78.8% effective in preventing symptomatic COVID-19. The heterologous boosters with BNT162b2 and AZD1222 were 96.5% and 93.2% effective, respectively.
Similarly, the effectiveness of the 3-dose homologous CoronaVac regimen against COVID-19–related hospitalization, intensive care unit admission, and death was 86.3%, 92.2%, and 86.7%, respectively. By comparison, the BNT162b2 booster was more effective at 96.1%, 96.2%, and 96.8%, respectively, while the AZD1222 booster was the most effective at 97.7%, 98.9%, and 98.1%, respectively.
Larkin HD. Mix-and-Match COVID-19 Boosters After Inactivated Virus Vaccine. JAMA. 2022;328(3):234. doi:10.1001/jama.2022.11844
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