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When it comes to the pandemic, it’s been a long winter — one of record-breaking COVID-19 infections and hundreds of thousands of lives lost. And throughout it, one thing has become clear: A booster shot is key to avoiding the ravages of the now-dominant omicron variant.
During December, unvaccinated adults ages 18 through 49 were 30 times more likely to be hospitalized than their boosted peers, federal data show. Looking at the 65-plus age group, the difference shoots up to 51 times more likely. What’s more, the risk of dying from COVID-19 during January was 41 times higher for unvaccinated adults than for those with their booster shot. “It’s very important to get boosted for omicron,” says David Montefiori, a professor and vaccine expert at Duke University School of Medicine’s Human Vaccine Institute.

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How long does this protection last? “There are no real clear definitive answers,” says Alessandro Sette, a professor at La Jolla Institute for Immunology. But scientists are learning more every day. Here’s what we know so far about the durability of a booster shot and what that could mean for the future.
Booster protection wanes, but still deters serious illness
If you’re one of the more than 93 million Americans who received a COVID-19 booster in the fall or winter and you are not immunocompromised, a number of experts say you are likely still well protected against serious illness and death. Still, it’s important to keep in mind that the vaccines offer “a gradient of protection” that is influenced by a number of factors, including age, genetics, the immune system and underlying health conditions, says Gregory Poland, M.D., professor of medicine and infectious diseases at the Mayo Clinic in Rochester, Minnesota, and founder and director of Mayo’s Vaccine Research Group. “There is no light switch here.”
Research collected during the omicron wave and published by the Centers for Disease Control and Prevention (CDC) found that about two months after a Pfizer-BioNTech or Moderna booster shot, the vaccine’s effectiveness against hospitalization was around 90 percent. Four months out, it was about 80 percent, which top infectious disease expert Anthony Fauci, M.D., says “is still a good protective area.” It’s also considerably higher than the level of protection against hospitalization provided by two standard doses of an mRNA vaccine, which fell to about 54 percent roughly five months after vaccination.
Despite the initial decline, scientists say the strong degree of protection against severe outcomes could hold steady even longer in some people. The reason? We’re learning more about the various players on the body’s COVID-fighting team and how they’re mounting their defense when faced with the coronavirus.