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The bivalent booster that targets the original coronavirus strain and the Omicron BA.4 and BA.5 subvariants became available in the US in early September. Pfizer and BioNTech said in a news release that the bivalent booster generated about four times higher levels of neutralizing antibody against the Omicron BA.4/BA.5 variants in people older than 55, compared with the original vaccine. The data has not been peer-reviewed or published.
When someone gets any vaccine, it can take a few weeks to build up immunity and generate its full protection. The data showed that a month after study participants got the new booster, Omicron BA.4/BA.5 neutralizing antibodies increased 13.2 fold from pre-booster levels for the adults 55 and older, compared with a 2.9 fold increase in older adults who got the original vaccine. For adults ages 18 to 55, neutralizing antibodies were 9.5 fold higher than pre-booster levels.
The Omicron BA.5 subvariant had dominated US Covid-19 infections since July, but a mix of other Omicron subvariants have been gaining against it. BA.5 now accounts for 49.6% of new infections in this country, according to data from the US Centers for Disease Control and Prevention.
“As we head into the holiday season, we hope these updated data will encourage people to seek out a COVID-19 bivalent booster as soon as they are eligible in order to maintain high levels of protection against the widely circulating Omicron BA.4 and BA.5 sublineages,” Pfizer CEO Albert Bourla said in a statement. “These updated data also provide confidence in the adaptability of our mRNA platform and our ability to rapidly update the vaccine to match the most prevalent strains each season.”
The companies’ new data comes after two small studies that measured immune responses about three to five weeks after the updated booster dose; both found that the updated Covid-19 booster shots appear to work about as well against the BA.4 and BA.5 Omicron subvariants as the original boosters they replaced. The studies were released as preprints and have not been peer-reviewed or published.
Pfizer and BioNTech are still conducting larger clinical trials of the updated boosters, and said they are continuing to test the vaccine against the other variants of the virus.
Experts say getting boosted this fall is still an important way to renew protection, even among people who were previously infected or vaccinated. People as young as 5 are eligible for updated boosters.
So far, 26.3 million people age 5 and older in the United States have received updated Covid-19 boosters.
An analysis released in early October suggested that if more people in the US got the booster by the end of the year, about 90,000 Covid-19 deaths could be prevented this fall and winter. However, if uptake of the vaccine continued at the pace of early October, the US could see a peak of more than 1,000 Covid-19 deaths per day this winter, according to the analysis from the Commonwealth Fund.