The U.S. is in a somewhat confusing place with the COVID pandemic right now. Just a month ago, infections were consistently dropping at significant levels, prompting officials to remove most restrictions. But now, they’re climbing up again: According to the Centers for Disease Control and Prevention (CDC), new coronavirus cases have increased by more than 35 percent in just the last week alone. Is this the start of a new surge, or simply the way things are now? For their part, health officials and virus experts have largely just agreed on one thing—the best way to protect yourself is getting vaccinated and getting boosted when eligible. The question of how many booster shots you need, however, is still an open one.
Anyone over the age of 50 in the U.S. can receive the fourth COVID shot now. Both the CDC and the Food and Drug Administration (FDA) amended their guidance on March 29 to make all adults 50 years old or older eligible for a second booster, as well as younger adults who are moderately or severally immunocompromised.
“Boosters are safe, and people over the age of 50 can now get an additional booster 4 months after their prior dose to increase their protection further,” CDC Director Rochelle Walensky, MD, said at the time. According to a Feb. 11 study from the CDC, the initial booster’s effectiveness against hospitalization falls to 78 percent after four months.
But there have been a number of debates surrounding the need for and timing of a second booster. This is in part because data from Israel—where officials began administering fourth doses of Pfizer to those over 60 in January—has found that the extra protection afforded by the additional dose appears to wane even faster than after the first booster. An April 6 study published in The New England Journal of Medicine found the second booster’s effectiveness starts to fall just a month after vaccination.
“The facts about the second booster that people need to understand to make that choice are that first, your immunity after that first booster wanes considerably four to six months out. That’s unquestionable,” Robert Wachter, MD, chair of the Department of Medicine at the University of California, San Francisco, told the Association of American Medical Colleges (AAMC). “The second booster raises your immunity about to the point where you were after the first booster. … Where it gets complicated is the length of protection.”
For the time being, the CDC has stopped short of definitively saying that all adults 50 and older should get a second booster. Instead, it is “up to you whether to get a second booster right now, based on the benefits and risks the vaccine may provide to you,” the agency says.
According to the CDC, there are two situations in which someone who is already eligible for a second booster may actually want to consider not getting the additional dose. One of these is if you have been infected with COVID sometime within the past three months.
“There’s a real immunological argument to be made for letting that immune response mature and develop memory cells,” Melanie Swift, MD, a physician and co-chair of the the COVID-19 Vaccine Allocation and Distribution Work Group at the Mayo Clinic, told Scientific American. “Two to three months after the infection would be a good window of time to get that booster.”
The other reason you might want to hold off on getting a second booster is if you think that getting this additional dose now would make you less likely to want to get another booster in the future. “A second booster may be more important in fall of 2022, or if a new vaccine for a future COVID-19 variant becomes available,” the CDC explains.
Overall, both this agency and other health experts recommend talking to your doctor about the fourth shot. “Your healthcare provider can help you review your options,” the agency says.
As the CDC notes, “certain factors can make it more likely someone will get very sick from COVID-19,” in which case you likely won’t want to delay getting another booster. These factors include underlying conditions, exposure risks, community spread, and living with someone who is unvaccinated.