Should You Get Another Covid Booster Now, or Wait Until the Fall?

An uptick in Covid-19 cases and the new school year have many people wondering when they should get their next booster. The short answer, according to experts: not quite yet — you’ll be a lot better off if you wait another few weeks.

In June, an advisory panel to the Food and Drug Administration recommended that the next Covid vaccine formulation target the Omicron XBB.1.5 variant.

Pfizer, Moderna and Novavax are now working to update, test and mass-produce their vaccines, which will then need to be officially authorized by the F.D.A. Experts estimate that shots will be available to the public by mid-September.

“For most people right now, it seems to me waiting makes more sense,” said Dr. Paul Sax, the clinical director of the division of infectious diseases at Brigham and Women’s Hospital.

There are two main reasons to hold out for the updated vaccine. First, it will be a better match for the variants that are currently circulating.

The majority of the coronavirus strains infecting people right now are either descended from, or related to, XBB.1.5, so the decision to target that variant with the vaccine “was about as good as you could imagine for the moment,” said Trevor Bedford, a professor in the vaccine and infectious disease division at Fred Hutchinson Cancer Research Center.

The vaccine will most likely also provide some protection against EG.5, which recently became the dominant variant in the United States, accounting for about 22 percent of current cases. EG.5 is descended from another XBB variant and has a few additional mutations, so antibodies produced by the updated vaccine may not be quite as effective against it. But the new booster is still a better fit for EG.5 than last year’s booster, which targeted both the original Covid strain and the BA.5 Omicron variant — neither of which appear to be circulating anymore.

Dr. David Boulware, a professor of medicine specializing in infectious diseases at the University of Minnesota Medical School, added that because the new vaccine is a better match for the current variants, he is “somewhat optimistic” that it will help prevent not only severe disease but also infection.

“Once you’re boosting with the variant that is closest to what’s actually circulating,” you will most likely regain some protection against infection, he said.

The second reason to wait for the new vaccine is that it will increase the odds that your defenses against the virus will be strongest when cases are expected to peak, historically between December and February. Antibodies wane over time, and protection is highest during the first three months following an infection or vaccination.

“Case numbers are increasing now, but they’re not at exceptionally high levels,” Dr. Sax said. “I can’t imagine, though, that they won’t go up again in November, December or January, as they did every single year in the past three years.”

If you’ve had Covid recently, experts suggest waiting a few additional months before getting the new shot. Your antibodies are already elevated because of the infection, and so the vaccine won’t provide you with much additional benefit during this time.

Vaccination is the only proven way to shorten a case of Covid, Dr. Boulware said. In a study published last year, he found that people who got Covid within six months of receiving a shot “had less severe disease and shorter duration of illness.”

If you’re worried about catching Covid in the meantime, use the behavioral protections you’ve employed throughout the pandemic: Avoid big crowds; wear a high-quality, well-fitting N95, KN95 or KF94 mask when you’re in indoor public settings; and try to make sure rooms are well-ventilated — even opening a window can help.