The first real-world data show that the bivalent booster is effective

Ion report published in Morbidity and Mortality Weekly Reportscientists from the US Centers for Disease Control and Prevention (CDC) have provided the first real evidence of the effectiveness of the bivalent booster shot, which the CDC and the US Food and Drug Administration (FDA) authorized in September.

The researchers concluded that the bivalent booster, which contains genetic material from both the original SARS-CoV-2 virus and the Omicron BA.4/5 variants, was effective in protecting people from severe COVID-19. The relative effectiveness among people aged 18 to 49 who received a bivalent booster—compared to those who received more than two shots of the original vaccine—ranged from 30 percent if their last initial dose of vaccine was two to three months, to 56% if their last initial vaccine dose was more than eight months before the new one. Effectiveness was slightly lower in older people, ranging from 28% to 48% among those 50 and older.

The fact that the vaccine’s effectiveness increased with more time than the last initial dose of vaccine showed that the new booster restored declining levels of virus-fighting antibodies, the researchers wrote.

Read more: You can still get free COVID-19 tests through insurance

The data comes from the national program to increase community access to testing, which provides 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 in nearly 1,000 locations, and people were asked to report their vaccination status and previous history of infection. During this time, the Omicron BA.4/5 variants were dominant, but newer variants, incl. BQ.1 and BQ.1.1which now represent nearly 50% cases in the US, began to increase. The researchers say that data during periods when only BA.4/5 dominated did not differ significantly in the effectiveness of the Omicron booster compared to periods when other variants appeared. Still, the researchers acknowledge that the results may change as newer variants take hold.

Other researchers are studying how the updated bivalent booster affects immunity—not only to the variants it targets, but also to earlier and potentially even newer variants that evolve from BA.4/5. some data suggest that vaccine-induced immunity may provide higher levels of virus-neutralizing antibodies than infection with the virus, 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 effective at recognizing and disabling the virus.

The 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 the circulation of BA.4/BA.5 and their sublines and restore the protection observed to wane after receiving a monovalent vaccine,” the study authors wrote.

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