Don't Get a Booster Shot Before You're Eligible — Here's Why

Getting a third dose booster shot is "a 'walk, don't run' situation," according to CDC director Dr. Rochelle Walensky. But some people may be sprinting ahead before they're actually eligible.

That's a mistake, experts say — for both yourself and the country's fight against Covid.

Roughly 5.7 million people, or about 3% of the fully vaccinated population, have received a third dose of a Covid vaccine since early August, according to data from the Centers for Disease Control and Prevention. The agency officially authorized Pfizer's third-dose boosters on Sept. 24, for adults 65 years and older, plus people ages 50-64 with underlying medical conditions and people 18 and up living in nursing homes.

A broader category of folks "may" get a booster, according to the CDC, depending upon their individual risks and benefits. That includes younger adults ages 18-49 who have underlying medical conditions and people ages 18-64 years old with jobs that raise their risk of Covid exposure.

As with the initial Covid vaccine rollout, you're responsible for declaring that you meet the criteria for a booster. In other words, as long as you wait six months after your second dose, you could theoretically jump the line and get a booster even if you aren't eligible — but you shouldn't.

"People just want their freedom back, and they're hoping boosters will make that happen," says Dr. Anna Durbin, an internal medicine infectious diseases trained physician, and professor of international health at the Johns Hopkins Bloomberg School of Public Health. "Boosters aren't going to make that happen. Vaccinating people who are not vaccinated is what's going to make that happen."

For most young and healthy people, "your benefit from a booster is limited," Durbin says. Here's why:

You're well protected by the two doses alone

If you got a two-dose mRNA vaccine and you're not currently eligible for a booster, you may never need that third dose.

Antibody levels decrease over time, and that's expected: Your body's memory immune response is still ready to defend you, if you encounter the virus again. "Your body can't spend all its energy making high levels of antibodies for every germ that you've ever seen," Durbin says.

Booster shots do increase those antibody levels, "but you don't need that now," Durbin says. "You want to save that for later."

The two doses still prevent severe illness, hospitalization and death from Covid, even in the face of variants like delta. Remember: Vaccines are not designed to prevent infection entirely. Rather, the goal of vaccination is to prevent severe disease, Durbin says.

"To expect the vaccine to prevent all symptoms is really unrealistic," Durbin says. "What we want to do is prevent severe cases and hospitalizations, because that's the human toll. That's the economic toll, and that's the public health infrastructure toll."

This guidance could change if vaccine-induced protection wanes to such a low point that it no longer reduces severe disease or prevent hospitalization and death, Dr. William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health, told CNBC Make It on Sept. 24.

The one exception: If you got Johnson & Johnson's one-shot Covid vaccine, you may be cleared for a booster shot relatively soon. On Tuesday, the drugmaker submitted data to the Food and Drug Administration for a booster shot of its one-shot Covid vaccine, which it says provides 94% protection against symptomatic Covid-19 in the United States and 100% protection against severe disease at least 14 days after the dose.

The FDA's advisory committee will meet to discuss J&J's booster shots, plus the "mix-and-match" approach of using an mRNA booster for one-shot recipients, on Oct. 15. If the FDA approves either one, the CDC will then determine specific guidelines for the rollout.

You'd make it harder for the CDC to track vaccinations

If you get a booster dose before you're eligible, you'll muddy the water for the CDC to accurately track how many people are vaccinated, Moss said. "It messes up the numbers if people aren't honest about it," he said.

That data is important: The CDC relies on it to make recommendations and guidance. If the agency thinks more people are vaccinated than they actually are, it could prematurely recommend loosening restrictions or dropping mask mandates, which could cause Covid infections to surge and new variants to emerge.

Fibbing your way to get a booster shot puts a wrench in the agency's ability to track vaccination rates at a population level, and potentially puts other peoples' lives at risk. Put simply, it's significantly more important for unvaccinated people to get vaccinated than for vaccinated people to get boosters.

You'll be better protected if you wait

Playing the long game and waiting until you're eligible to get a booster comes with at least one potential perk: Boosters might be more advanced and targeted for specific variants down the line.

"There could be new variants that arise, that could come into the United States, in which case we may need a booster," Durbin says. "But only time is going to tell us that."

The most likely such scenario, according to Moss, is if a new variant emerges that evades vaccine-induced immunity. That would lead to "revaccination with a reformulated vaccine," similar to the way the influenza vaccines change each year based on the strains that circulate, Moss said.

As long as the virus circulates in unvaccinated populations around the world, new variants could emerge and make their way to the U.S. — which is all the more reason to focus on getting shots into unvaccinated people's arms.

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