COVID-19 boosters from Moderna and the partnership of Pfizer and BioNTech that fight the latest omicron variants provide only modest short-term protection against mild infections, and experts say it’s still unclear whether the updated shots are any better than earlier versions at preventing hospitalization and severe illness.
The bivalent boosters were just 43% effective at preventing mild illness compared to receiving no vaccine in adults 49 and under, according to a U.S. Centers for Disease Control and Prevention study published Tuesday. In those aged 50 to 64 years, comparative protection against symptomatic COVID-19 was 28%, while the booster was just 22% protective in adults 65 and older, the study showed.
Younger, vaccinated people benefited most from the shots that fight the BA.4 and BA.5 omicron strains, according to the study that offers a glimpse at how the updated shots perform in the real world. For older people, protection was lower against mild illness, but still much better than being unvaccinated.