As pressure mounts on the Food and Drug Administration to grant formal approval to Pfizer's Covid-19 vaccine, doctors and public health experts across the country say it's still unclear what impact, if any, such approval would have on patients and providers.
One hope is that full approval could convince those who are vaccine hesitant that the shots are safe. A survey in June from the Kaiser Family Foundation, for example, found that 3 in 10 unvaccinated adults would be more likely to get the shots if one of the vaccines received FDA approval.
"People are going to see full approval, and they are going to feel much more confident in taking the vaccine," said Dr. Robert Murphy, executive director for the Institute of Global Health at Northwestern University's Feinberg School of Medicine.
Murphy said some of the lack of confidence in a vaccine that has received only emergency use authorization lies in a misunderstanding of what that type of authorization means.
"It does not mean it's experimental. All the experimental work has been done," he said.
Others agreed that FDA approval could boost some people's confidence but cautioned that the overall effect is likely to be small.
"I don't think it's going to have much change at all," said the president of the American Academy of Family Physicians. Dr. Ada Stewart, a community clinic doctor in Columbia, South Carolina. "Maybe it will increase confidence."
Dr. Jesse Goodman, an infectious disease specialist at Georgetown University Medical Center, said there is too much misinformation driving vaccine hesitancy to change most opinions.
"I think maybe on the perception side, some people who felt this was an extremely or quickly developed product, only developed for emergency use — there might be some people who have more confidence," Goodman said. "Although I wouldn't overestimate that."
Indeed, the same Kaiser Family Foundation survey also found that two-thirds of adults, including many of those who were unvaccinated, believed that all three vaccines available in the U.S. were either already approved or that they were unsure whether they have been or not.
Still, public health experts say full approval could also help companies and cities with vaccine mandates, which are becoming more common but are still surrounded by controversy.
"I think a lot of large enterprises, public and private, are waiting for approval to mandate vaccines for students and employees," said a former FDA associate commissioner, Peter Pitts, president of the Center for Medicine in the Public Interest, a nonprofit advocacy group.
And there are other more concrete changes that come with full FDA approval.
One is the ability to prescribe a medication "off label" — a common practice in which doctors prescribe approved drugs for unapproved uses. For example, the diabetes drug metformin is sometimes prescribed for weight loss because one of its side effects is to lower a person's appetite.
The practice is legal under FDA guidelines, as long as a patient's doctor judges that "it is medically appropriate for their patient."
Off-label use is not allowed for drugs granted emergency use authorization, however. Under an emergency authorization, a medication can be used only in the specific circumstances outlined in the authorization.
Experts say, technically, yes. But should they? That's more complicated.
"As an approved product, like all medical products, it can be used off label at the discretion of a health care provider and the patient," said Goodman, who is also a former chief scientist of the FDA and a former director of the agency's Center for Biologics Evaluation and Research. "But that could have some complicated effects."
Goodman said little safety data is available yet when it comes to Covid booster shots, so doctors would be taking a risk.
"I think most would follow the recommended approvals from the FDA and what's been recommended" by the Advisory Committee on Immunization Practices, he said, referring to the Centers for Disease Control and Prevention's panel of independent advisers that helps set vaccination guidelines. "But clearly not all. There are people who get strong beliefs or if a patient or family member pressures a doctor, they may say OK. It does open the door for some problematic uses."
The FDA declined to comment on using approved vaccines off label for boosters. A spokeswoman, Abigail Capobianco, said in a statement: "Americans who have been fully vaccinated do not need a booster shot at this time. FDA, CDC, and NIH are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary."
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Even more concerning is that doctors may give a vaccine off label to children under 12, a group that is still being studied, Pitts said.
"When you use a vaccine off label, you're playing with fire, because you don't have the data, and that's not a good idea," Pitts said, adding that when medications are used for unapproved uses, some supporting data are typically already available.
"Vaccinating anybody without data to support that decision is a risky proposition, and it shouldn't happen," he said.
But anecdotal reports suggest it's already happening, particularly among fully vaccinated adults seeking additional doses. On Twitter, Dr. Eric Topol, a physician-scientist at Scripps Research in California, said he's seeing the start of "booster-mania," with people going to drugstores and lying about their vaccination statuses.
Besides the health risk, Murphy warns that there could be a legal risk.
Murphy said that because the U.S. government purchased all of Pfizer's doses, it technically owns them. Patients trying to get third doses or doctors giving boosters by tricking the system could be committing fraud.
"If the vaccine is technically owned by the U.S. government, then that's fraud," he said. "You're defrauding the government. But if Pfizer sells to private offices, then there's nothing they can do."