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January 26, 2023

Bivalent boosters offer protection against the latest COVID-19 variant, CDC study finds

Only 15% of eligible Americans have received the shots. To spur interest, the FDA has proposed limiting boosters to once per year

Getting a bivalent booster shot nearly cuts in half the risk of getting sick from the most common COVID-19 variants, according to a new study by the U.S. Centers for Disease Control and Prevention. 

People who received boosters are nearly 13 times times less likely to die of COVID-19 than people who are not vaccinated, the new data show. They are two times less likely to die when compared to people who had at least one shot from the original COVID-19 vaccine series, but have not been boosted.

The boosters from Moderna and Pfizer work well against XBB.1.5, the highly transmissible omicron subvariant, which accounts for nearly half of all COVID-19 cases in the United States, the CDC says. The World Health Organization has called XBB.1.5 the most transmissible variant yet.

The bivalent boosters were specifically designed to target the omicron variants, thereby offering better protection than the original shots. But only 15.3% of eligible Americans have received them, the CDC says

In an effort to streamline vaccinations and encourage more people to get boosted, the U.S. Food and Drug Administration has proposed rolling out annual COVID-19 shots each fall. Just like flu shots, the annual booster would be updated to match whichever variants are circulating. 

"I don't think that we can chase after every new variant that comes along because the virus is changing so much," Dr. Stanley Perlman, an immunology professor at the University of Iowa who serves as an FDA adviser, told Bloomberg. "It makes it harder to convince people because if someone doesn't want to get a shot every four months, the response might be 'Well, I'm not going to get a shot at all.'"

Among adults ages 18 to 49, the current boosters offer 48% protection against symptomatic infections caused by the XBB.1.5 and SBB subvariants, the CDC study found. But older adults have less protection. The shots are 40% effective in adults ages 50 to 64, and 43% effective in adults age 65 and older. 

That protection lasts at least two to three months, but it may last longer. 

"It's too early to know how waning will happen with the bivalent vaccine," Ruth Link-Gelles, one of the study authors, told Politico. "What we've seen in the past is that your protection lasts longer for more severe illness. So even though you may have diminished protection over time against symptomatic infection, you're likely still protected against more severe disease for a longer period of time."

Though COVID-19 cases have fallen slightly in January, deaths have risen. On average, 564 people died of COVID-19 each day through Jan. 18. At the same point in December, the average number of daily deaths was 384. 

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