Recent data suggests that protection from Covid-19 booster shots wanes after a few months, potentially signaling a need for an additional, fourth dose of the vaccine in the future, Sharon LaFraniere reports for the New York Times.

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How long does booster protection last?

According to several recent studies, the protection offered from Covid-19 booster shots is likely short-term, waning after a few months.

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For example, data released last month by the U.K. Health Security Agency suggests that protection from infection offered by a booster dose of Pfizer-BioNTech's Covid-19 vaccine lasts less than six months. Researchers found that protection against symptomatic infection was relatively high after two weeks at 70% but decreased significantly by three months to around 50%.

However, the researchers also noted that protection against severe disease remained relatively robust over time—beginning at around 95% and remaining around 80% even after four months.

Similarly, a CDC study released earlier this month found that immunity against Covid-19 from booster doses declined significantly after around four months. In the study, researchers examined 241,204 ED/urgent care center visits and 93,408 hospitalizations in 10 states from August 2021 to Jan. 22, 2022, covering periods when delta and omicron were dominant. Around 10% of people in the study were boosted.

Overall, researchers found that booster protection against hospitalization from the omicron variant declined from 91% after two months to 78% after four months. In addition, protection against ED or urgent care visits declined from 87% to 66% after four months.

Despite the study's limitations, such as variations by age group, underlying medical conditions, or potential immune deficiencies, the researchers said the findings suggest a fourth Covid-19 vaccine dose may be necessary in the future.

Will a fourth dose be needed?

Although data suggests booster effectiveness declines after a few months, federal health officials said they do not currently plan to recommend fourth doses of the Covid-19 vaccine, LaFraniere writes.

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"We simply don't have enough data to know that [recommending a fourth dose is] a good thing to do," said Peter Marks, head of FDA's vaccines division.

Separately, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said the vaccines still offer strong protection against severe illness, even if CDC data suggests there is a slight decline after a few months. "'Should I get a fourth shot?' That's what a lot of people are asking me," he said. "The answer is if you look at where we are now, it looks like it's good protection. Seventy-eight percent is good."

Fauci added that the federal government's vaccine strategy going forward will depend on whether protection from boosters remains at current levels or continues to drop over time—and by how much. "It's not only the number, it's the inflection of the curve," he said.

However, Marks said it's possible an additional dose will be recommended in the fall when transmission of the coronavirus is expected to increase again. "Barring any surprises from new variants, maybe the best thing is to think about our booster strategy in conjunction with the influenza vaccine next fall, and get as many people as possible boosted then," he said.

According to Fauci, it is also possible that the recommendation for an additional dose would only be targeted towards certain groups who are most at risk of severe Covid-19 outcomes, such as older adults or those with underlying conditions.

"I don't think you're going to be hearing, if you do, any kind of recommendations that would be across the board for everyone," Fauci said. "It very likely will take into account what subset of people have a diminished, or not, protection against the important parameters such as hospitalization." (LaFraniere, New York Times, 2/18)