The updated Covid boosters reduce the risk of Covid infection from the predominant omicron subvariant by nearly half, according to early data released Wednesday by the Centers for Disease Control and Prevention.
The latest boosters from Pfizer-BioNTech and Moderna were 48% effective against symptomatic infection from the XBB in adults up to age 49. The new report said 1.5 was a subvariant. As of Jan. 21, that subvariant accounted for about 1 in 2 new cases in the United States.
In older groups, the boosters were 40% effective in adults ages 50 to 64 and 43% effective in people 65 and older.
Brendan Jackson, head of the CDC's Covid response, said on a call with reporters on Wednesday that the findings are quite reassuring. These updated vaccines are intended to protect people against the latest Covid 19 variant. The boosters of Covid were modified in the summer to target the BA. In 2019 in Wuhan, China, 5 omicron subvariants were identified as the original strain of the coronaviruses.
In the fall, 5 was the dominant variant in the U.S. but now accounts for only 2% of new cases.
According to the data released by the CDC, only about 15% of people in the U.S. had received an update booster.
With this data, we see there is a benefit that might be convenient for some people to sign up and get a bivalent booster, said Peter Hotez, co-director of the Center for Vaccine Development at Texas Children's Hospital and the Dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.
The CDC report is based on the test results from more than 29,100 adults with Covid symptoms who were tested at pharmacies nationwide from December 1 to Jan. 13.
People who had received the updated booster but had not received the updated booster were compared to those who had received the updated booster in the previous two to three months. Ruth Link-Gelles, who heads the vaccine effectiveness program, said on the call that those who hadn't received the updated booster had their last vaccine dose about 13 months ago.
The booster's protection is on par with what's usually seen with the flu vaccine. Flu vaccine effectiveness varies from season to season, but the shots reduce the risk of the flu by between 40% and 60%, according to the CDC.
Greg Poland, the director of the Mayo Clinic Vaccine Research Group in Rochester, Minnesota, cautioned that the CDC's estimate on the updated boosters may be an overestimate.
He said that people who got the boosters are probably more likely to wear masks indoors or restrain their travel or not go to indoor restaurants.
He pointed out that the CDC's data doesn't capture people who have been vaccinated with the updated booster but are asymptomatic, or people who were sick enough that they went to the hospital.
Hotez said he'd like to see how well the boosters perform against symptomatic infections after five or six months, while the CDC's findings appear promising.
He said he'd like to see more data on how well the boosters work against hospitalization.
Jackson, of the CDC, said on the call that the updated boosters have reduced the risk of death from Covid by nearly thirteenfold, compared to people who are unvaccinated.
People who got the booster had more than twofold lower death rates from Covid compared to people who didn't get it, he said.
The CDC's report comes a day before a meeting of the Food and Drug Administration advisory committee that will discuss simplifying the Covid vaccine schedule.
In a document posted online Monday, the FDA proposed using the bivalent formula in all Covid vaccines moving forward, not just for booster shots.