The U.S. plans to authorize boosters—but many already got a third dose

Here’s what we know about waning immunity and the science supporting the booster shot.

News of SARS-CoV-2 slipping past the protection of COVID-19 vaccines, infecting more than 300 fully vaccinated Massachusetts residents, shook Tampa Bay resident Crystal Gorges. But it was her stepfather’s hospitalization that broke her: After her fully vaccinated relative contracted COVID-19, Gorges drove on August 9 to her local grocery store and requested an mRNA vaccine.

It was the 47-year-old’s third COVID-19 shot.

“It’s kind of like the Wild, Wild West here,” says Gorges, citing Florida’s soaring coronavirus case load and its lack of mask mandates. “And I just want to be extra safe.”

Gorges is one of more than one million Americans who received additional doses of COVID-19 vaccines before the U.S. Food and Drug Administration on August 12 authorized additional shots for the most seriously immunocompromised Americans. A day later, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) voted unanimously to recommend the extra dose.

As recently as last week, Janet Woodcock, the FDA’s acting commissioner, said that most adults “who are fully vaccinated are adequately protected and do not need an additional dose of COVID-19 vaccine at this time.” But on August 18, the Biden administration said it plans to begin rolling out booster shots—starting first with those in nursing homes, on the front lines of health care, and the elderly—on September 20.

In a joint statement, the nation’s top public health officials said that Americans who have received the Moderna and Pfizer vaccines will be able to get a booster shot eight months after a second dose. First, however, the FDA must authorize the use of additional shots for the general population. Pfizer-BioNTech on Monday submitted phase-one data of their booster shot to the FDA.

The announcements come on the heels of other countries—among them Germany, France, and Israel—rolling out booster doses to wider swaths of their populations, and after the World Health Organization called for a moratorium on boosters until more people can get first doses.

The FDA and CDC recommend that fully vaccinated Americans who have had solid organ transplants—or who have a condition that creates an equivalent level of immune impairment—to seek a third shot of an mRNA vaccine. It does not apply to those who received the one-dose Johnson & Johnson vaccine, nor to Americans who are not severely immunocompromised.

But as the Delta variant rages across the U.S. and concerns rise over waning immunity against COVID-19, many Americans have jumped the proverbial booster line, taking their healthcare into their own hands as millions of vaccine doses languish unused.

The practice has ignited medical and ethical debates over the use of extra doses, with some experts warning it’s too soon for Americans to self-prescribe booster shots—and others worrying these announcements will encourage even more people to offer up their arms before it’s their turn.

According to the ACIP’s guidance, a doctor’s note or proof of prescription isn’t necessary to receive an additional dose of an mRNA vaccine. As of now, people need only say that they are immunocompromised to get an extra shot. “We’re trying to not make this a complicated process to roll out and for public health authorities to be able to implement,” says Wilbur Chen, a professor of medicine at the University of Maryland School of Medicine and a voting member of the ACIP.

But he also admits that the guidance creates a “bit of a loophole” that could encourage healthy adults to say that they have a weakened immune system in order to get a shot sooner.

“I think humans will be humans, and people will get away with whatever they can get away with,” says Jerome Singh, an adjunct professor of clinical public health at the University of Toronto and member of various WHO committees, including its Ad Hoc Research Ethics Review Committee for COVID-19. “That’s how the world works.”

What we know about boosters

Chen says that the available data is “very convincing” that immunocompromised people can benefit from booster doses of mRNA vaccines. But the data is a little fuzzier for other American adults.

A study published last week found the Pfizer-BioNTech mRNA vaccine is 88 percent effective at preventing symptomatic infections from the Delta variant, while a preprint study found that a single shot of Moderna’s two-dose mRNA vaccine offers 72 percent effectiveness against Delta.

Most people “continue to derive tremendous value from being vaccinated,” Chen says.

But last month, the Israeli government released data that indicated vaccine effectiveness drops over time; and a subsequent study from Israel, which has not yet been peer reviewed, found “the risk for [COVID-19] infection was significantly higher for early vaccinees compared to those vaccinated later,” perhaps signaling waning immunity.

“Vaccine effectiveness is expected to wane” over time, says Akiko Iwasaki, a professor of immunobiology and epidemiology at Yale School of Medicine.

“Booster shots are normal,” she says. While the immune system’s pathogen-fighting memory cells “are very long lived,” she says, “and they remember the antigens that they encounter the first time, they [memory cells] still need a little bit of encouragement every once in a while.”

Pfizer-BioNTech, a for-profit company, is testing a booster given six months after a second dose. While the clinical trial is ongoing, the companies have reported the booster produces as many as 10 times more neutralizing titers against the original SARS-COV-2 and its Beta variant than the primary doses.

In its second-quarter earnings report, Moderna, also for-profit, said that “robust antibody responses have been observed from existing Moderna booster candidates against COVID-19” in phase-two studies.

That hasn’t stopped many Americans from getting boosters, though.

Rochelle Walensky, CDC director, has said the organization has started to track the number of unauthorized booster shots across the country. Initial data indicates that of the 139.5 million Americans who have completed a two-dose regimen, about 1.14 million of them have received one or more additional shots; and of the 12 million people who received the one-dose Johnson & Johnson vaccine, just shy of 91,000 have received one or more additional vaccine doses.

Self-prescribed boosters

Delta has driven a spike in COVID-19 cases across the country, with more than 140,000 cases—and more than 80,000 hospitalizations—each day for the past week. “People are extremely alarmed,” Chen says, and that fear may be driving others to seek out additional vaccine doses.

But while many assume “that after a booster dose you will be more protected than prior to a booster dose,” says Dan Barouch, a virologist at Beth Israel Deaconess Medical Center, it’s too soon to know. “That very well might be true,” Barouch says, “but it still remains to be shown.”

Those who jump the line (and the gun) may also not reap all the potential benefits of a booster.

For instance, studies are still exploring the optimal timing for a booster shot—a sweet spot that ensures the strongest immune response. Getting a booster too soon after primary inoculation might not teach the body’s immune system to mount a more robust defense, Iwasaki explains.

And while the CDC’s Walensky encouraged people who get booster shots to self-report safety outcomes, there’s no guarantee they will. That potential lack of data could “undermine our ability to monitor safety in these contexts,” Walensky told reporters at an Aug. 2 press briefing.

Ongoing studies are monitoring the effectiveness of using a booster different from the original shots—following a Johnson & Johnson vaccine with an mRNA vaccine, for example, or taking a dose of Moderna after receiving two doses of the Pfizer-BioNTech vaccine. But Iwasaki warns it’s too soon for people to mix-and-match their doses in the real world. “We shouldn't be mixing and matching just willy-nilly, multiple times,” Iwasaki says. “That's not a good idea.”

She adds that, “I know that there's a lot of fear out there. But at the same time, scientists are also working around the clock to try to figure out what is the best” timing, mix, and dosage.

For people who are not immunocompromised, she says, “the best thing to do right now is to wear a mask, avoid crowded indoor spaces, wash your hands—do all the things we’re used to doing, and wait for a recommendation to get the third shot if we need it, or when we need it.”

Helping others to help ourselves 

As Jamie Hickey thought about his seven- and nine-year-old daughters returning to school, he worried for their health—so he asked his healthcare provider to give him a booster shot in early August.

“They can’t get vaccinated,” the 42-year-old Philadelphia resident says, “so I figured I would do as much as I could for them.”

But World Health Organization Director General Tedros Adhanom Ghebreyesus has asked wealthier countries to suspend booster doses, for now, even to protect their own citizens.

“We cannot—and we should not—accept countries that have already used most of the global supply of vaccines using even more of it, while the world’s most vulnerable people remain unprotected,” he said during an Aug. 4 press briefing. Data shows that only 1.3 percent of people in the lowest income countries have received at least one dose of a COVID-19 vaccine.

“There’s no question that personal responsibility—to yourself, to your family—is in tension with our responsibility as a society to other countries,” says J.P. Leider, a bioethicist at the University of Minnesota. “I don’t really blame people who are seeking further protection. The problem is that when all these individuals act a little selfishly, that dramatically decreases the ability for people across the globe to get a first shot as opposed to a third shot. And that’s a profound injustice.”

So far, the Biden administration has pledged to donate 500 million vaccine doses to other countries.

The strategy of “grabbing what you can get and holding tight [is] failing us,” says Nancy Jecker, a professor of bioethics and humanities at the University of Washington School of Medicine.

She says that allowing millions to go unvaccinated “creates pathways for the virus to replicate and mutate, and that endangers everyone, including the vaccinated, rich and poor alike.”

Gorges says she thought hard before getting her booster. But, “it doesn't seem that we’re really giving any of our vaccines away,” she says. “They’re just sitting there.”

But Singh, who sits on the WHO’s Ad Hoc Research Ethics Review Committee for COVID-19, says that every vaccine dose used by an American “represents an opportunity cost. It’s an opportunity cost for somebody in a low- or middle-income country to get that same dose.”

And while Jecker understands people’s fear, she adds that they must look past it for the greater good. “We have a knee-jerk reaction; we think we need everything we can get to stay alive and safe,” she says. “But ultimately, we’re harming ourselves as well as others when we use that approach: We’re all going to be vulnerable as new variants emerge.”

Editor’s note: This story was originally published on August 17. It has been updated to note the Biden administration’s announcement on booster shots.

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