The bivalent amplifier is an efficient, first representation of real-world data

Ireport published in Morbidity and Mortality Weekly Reportscientists from the US Centers for Disease Control and Prevention (CDC) provided the first real evidence of the effectiveness of the bivalent vaccine, which was approved by the CDC and the US Food and Drug Administration (FDA) in September.

The researchers conclude that the bivalent booster, which contains genetic material from both the original SARS-CoV-2 virus and the Omicron BA.4/5 variant, is effective in protecting people from the severe disease of COVID-19. Relative effectiveness among 18- to 49-year-olds who received a bivalent booster—compared with those who received more than two injections of the original vaccine—ranged from 30% if their last original vaccine dose was two to three months ago, up to 56% if their last original dose of vaccine was more than eight months before the new one. Effectiveness was slightly lower for older people, ranging from 28% to 48% among those 50 and older.

The fact that the effectiveness of the vaccine increased with more time since the last original dose of the vaccine indicates that the new booster is compensating for declining levels of antibodies that fight the virus, the researchers write.

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The data came from the national Increasing Community Access to Testing program, which offers free COVID-19 tests at pharmacies across the country. Between September 14 and November 11, more than 360,000 SARS-CoV-2 tests were performed at nearly 1,000 locations, and people were asked to report their vaccination status and previous history of infections. During this time, Omicron variants BA.4/5 were dominant, but newer variants, including BQ.1 and BQ.1.1, which now account for nearly 50% of cases in the US, began to rise. The researchers say that the data in the periods when only BA.4/5 dominated did not differ significantly in terms of the effectiveness of the Omicron enhancer compared to the periods when the other variants appeared. However, the researchers acknowledge that the results may change as newer variants take over.

Other researchers are investigating how the updated bivalent enhancer affects immunity—not just the variants it targets, but also previous and even potentially newer variants that develop from BA.4/5. Some data suggest that vaccine-induced immunity may provide higher levels of virus-neutralizing antibodies than viral infection would, possibly because the immune system sees and responds to vaccines differently than it sees and responds to pathogens such as viruses. And any vaccination can also help the immune system become more efficient at recognizing and neutralizing viruses.

Current real-world findings, the study authors say, point to the need to stay up-to-date on COVID-19 vaccines, including getting the latest Omicron booster. Bivalent boosters “provide protection against symptomatic SARS-CoV-2 infection during circulating BA.4/BA.5 and their substrates and restore protection that was observed to wane after receipt of monovalent vaccine,” the study authors write.

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