What we know about COVID vaccine booster shots — and when we may need them

Now that almost half the U.S. population is fully vaccinated against COVID-19, many people are beginning to wonder how long that protection will last, and if they will need a booster shot down the road.

At the moment, there are more questions than answers surrounding the possibility of needing an additional dose of the COVID-19 vaccines to boost immunity over time. Dr. Betty Diamond, director at the Feinstein Institutes for Medical Research in Manhasset, N.Y., said more studies are needed to determine if and when a booster will be necessary.

“Vaccines are fickle or idiosyncratic,” she told Yahoo News. “So you can't predict how long immunity is going to last when you develop a vaccine.”

Diamond explained that certain inoculations, such as the polio vaccine, provide lifelong immunity against that disease, while others, such as tetanus or flu shots, generate defenses that can wane over time. To be fully protected against tetanus, for example, the Centers for Disease Control and Prevention recommends getting a booster every 10 years; for the flu, it is advised to receive a shot every year.

“We don't have the information that we need about the SARS-CoV-2 vaccines,” she said.

However, some health authorities, including Dr. Anthony Fauci, the nation’s leading infectious disease expert, foresee that boosters will be necessary. “I don't anticipate that the durability of the vaccine protection is going to be infinite,” Fauci told a Senate subcommittee on May 26. “I would imagine we will need, at some time, a booster,” he said, adding that he was “not exactly sure when” it would be needed.

In an Axios interview last month, Pfizer CEO Albert Bourla said the data he was seeing so far supported “the notion that there will likely be a need for a booster somewhere between eight and 12 months.” He added that for the first wave of Americans who were vaccinated, booster shots could be needed as soon as September or October.

Although experts are not exactly sure how long the COVID-19 vaccines offer protection, they believe it may last at least six months and likely a year. Some studies have analyzed blood samples from the first people who were vaccinated in the trials to measure their levels of antibodies and immune cells that fight off the coronavirus. One such study, published by the New England Journal of Medicine this month, found that antibodies elicited by the Moderna vaccine remained strong for at least six months.

It may be reassuring to know that scientists are working to determine whether COVID-19 vaccine boosters will be needed and that the government is preparing early for that possibility. The National Institutes of Health recently announced it would be conducting a new clinical trial of people fully vaccinated with one of the authorized vaccines to see whether a booster of the Moderna shot will increase their antibodies and prolong their protection against the virus.

Vaccine makers such as Moderna, Pfizer and Johnson & Johnson are also working on developing and testing booster shots in trials.

Yahoo News Medical Contributor Dr. Kavita Patel said that early data suggests some people, particularly the elderly, the immunocompromised and those who have had solid-organ transplants, may need boosters “sooner rather than later.” This is because “they demonstrate lower levels of immunity, even with the current vaccines. So there might need to be a prioritization for those populations with boosters,” she said.

Another important question is whether people will need booster shots tailored for specific variants. That is not clear yet, but some scientists suspect that the vaccines that elicited a high immune response to the original version of the coronavirus will continue to provide sufficient protection against variants as well. Patel said the current vaccines so far protect against these emerging variants of concern around the world, but “some to a lesser degree than the variants we had a year ago.”

In a study published last month, for example, researchers in Qatar looked at the effectiveness of the Pfizer-BioNTech vaccine — administered to more than 250,000 of the country’s residents between December and March — against the B.1.1.7 and B.1.351 variants. These, which have now been designated as alpha and beta by the World Health Organization’s new naming system for coronavirus variants, were predominant within the country at the time of the study. The study found that even though the vaccine was 100 percent effective at preventing severe disease, effectiveness against both variants was lower than that reported in the clinical trials.

In the Pfizer clinical trials, the vaccine showed an efficacy of 95 percent against the original version of the coronavirus. But according to the study, the variant called alpha, first identified in Britain, lowered the effectiveness to 89.5 percent. And the variant known as beta, which was first identified in South Africa, lowered the vaccine’s effectiveness to 75 percent.

Perhaps having a booster designed to target one variant in particular could be more effective, but that is currently being investigated. Pfizer has begun trials to test both options — a booster targeting the original form of the virus as well as one designed to protect against the beta variant.

Finally, some people are wondering if it will be safe to switch vaccine brands if boosters are needed. Diamond said trials are underway to determine if this is possible.

“The actual antigen from SARS-CoV-2 is the same in all of these vaccines,” she said. “So the memory cells that you generated are going to be able to see it in the new vaccines, or in the alternative vaccines. I think the expectation is that it's not going to be a problem to mix and match.”

The bottom line, Diamond told Yahoo News, is that even though there is a lot to learn about COVID-19 booster shots, the current vaccines in the U.S. are “amazing,” and people should take advantage of the protection they offer.

“Vaccines are one of the jewels in the crown of medicine, and we should take advantage of them — like we take advantage of antibiotics when we need them,” she said.


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