Your Booster Will Only Protect You for This Long, New Study Shows

Researchers from the U.K. gave new insight into the duration of COVID booster protection.

The Omicron variant is infecting thousands of people every day in the U.S., from first-time cases to breakthrough infections and reinfections. Virus experts have been advocating for booster shots as the fast-spreading variant continues to circulate, with boosters now being referred to as the "optimal protection" against Omicron. Copious studies have shown that protection from just one or two vaccine doses wanes significantly over time, and in the face of new COVID variants. Now, experts are debating just how many additional doses might be needed over time—and that all depends on how long protection from your current booster lasts.

RELATED: Dr. Fauci Says Wait to Get Your Booster Shot If You've Done This.

Researchers from the U.K. just released a new report on Jan. 14 recounting results of a study that analyzed the long-term protection of a third shot of the Pfizer vaccine by observing more than 700,000 Omicron cases. According to the U.K. Health Security Agency (UKHSA), the results showed that two weeks after the shot, Pfizer's booster cuts the risk of symptomatic infection against COVID by about 70 percent.

But in terms of the length of protection, results were less favorable. The same analysis found that protection appears to fall quickly, and by three months, the booster reduces the risk of symptomatic infection by only about 50 percent. A second analysis from the U.K. researchers indicates that the protection is likely to decline even further after this. According to the report, it is estimated that protection will drop to around 40 percent just four months after a booster dose.

Based on these results, Michaeleen Doucleff, a global health correspondent for NPR, explained in a Jan. 19 All Things Considered podcast that booster protection against infection appears to be rather short term. "Overall, it will likely last less than six months for most people," she said.

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Other experts caution against taking this as bad news. Jennifer Gommerman, PhD, an immunologist at the University of Toronto, told NPR that is is "perfectly normal and expected" that with any vaccine—even the booster—antibody levels rise quickly right after the shot and then diminish over time, which affects protection against infection in particular.

"The vaccine's efficacy against infection relies on our level of antibodies because they are really our first line of defense against SARS-CoV-2," she explained. "So in terms of protection against infection, we will see some protection early on with a booster, but that protection is going to wane."

At the same time, vaccine protection against severe disease does not depend as heavily on antibodies, according to Gommerman. "So with declining antibody levels, you might be vulnerable to an infection but not necessarily vulnerable to disease—that's a different kettle of fish," she said.

This falls in line with what the U.K. researchers found in their study. According to their analysis, protection against hospitalization is higher than 95 percent two weeks after a third shot of Pfizer and even after four months, it remains at an effectiveness of around 80 percent. In the wake of Omicron, that's a particularly stark difference compared to just two shots of the vaccine, where protection against severe disease declines to around 40 percent after six months.

RELATED: If You Have Omicron, This Is When You'll Begin to Feel Symptoms.

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