covid-19 coronavirus booster vaccination needle

The updated COVID booster vaccines are 43% effective against symptomatic infection from the XBB subvariants in adults aged 65 years and older, and 37% effective against BA.5 in that age group, a federal study shows.

The two bivalent mRNA booster shots, from Pfizer-BioNTech and Moderna, were developed using a component of the original COVID-19 vaccines and a new component that better targets omicron subvariants. They were federally authorized as the preferred booster shots in August 2022. 

The study followed national pharmacy testing data from December 2022 to January 2023. Results showed that a booster dose provided protection against symptomatic XBB and XBB.1.5 infections for “at least” three months in people who had previously received two to four monovalent vaccine doses, federal researchers reported. Prior to this study, the booster shots’ efficacy had been determined by laboratory tests.

The new report includes the first estimates of the shot’s ability to protect against symptomatic SARS-CoV-2 infection with XBB-related sublineages, the researchers said. These omicron-related subvariants are known to spread quickly and are becoming a dominant cause of infections in parts of the United States.

“Today we have additional evidence to show that these updated vaccines are protecting people against the latest COVID-19 variants,” Brendan Jackson, MD, of the Centers for Disease Control and Prevention, said in a Wednesday briefing, according to Reuters.

Among younger adults, protection against symptomatic XBB/XBB.1.5-related infection was in the same range as seniors, at 49% in the 18-to-49 age group and 40% among people ages 50 to 64 years.

In the briefing, health officials said that the data also lowered the risk of death from COVID-19 more than twofold when compared with people who were vaccinated, but had not received the updated booster, Reuters reported. The risk of death from COVID-19 fell by nearly 13-fold in unvaccinated people, the news outlet added.

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