The protection against infection from booster doses wanes quickly, in just a couple of months, so a booster shot now will not offer much defense in August or even July.

It takes the immune system about a week to rev up after the shot. From that peak, antibodies taper down over the next two to three months. So if you qualify for a booster, you may want to have the maximum protection right before your trip — or before the next surge.

“The one thing that matters is where we are in this whole pandemic,” Dr. Pepper said. “I would be watching what the variants are doing.”

Late last year, when the Omicron variant was ubiquitous, getting a booster made sense simply to prevent infections.

Dr. Wherry, who is 50, said he opted for a third dose even though he was not worried about becoming sick because getting infected would have been “extremely inconvenient” for his work and for his two children in high school.

“Right now as a healthy 50-year-old, I don’t see any need for a fourth dose,” he said. But he might revisit that choice if the case numbers tick up again.