A Pfizer COVID-19 vaccine is administered at a mobile clinic in Los Angeles county, which has pockets of vaccine hesitancy.

Irfan Khan/Los Angeles Times via Getty Images

In many U.S. regions, the Delta variant of SARS-CoV-2 has caused the COVID-19 pandemic to surge once again. Last week’s 7-day average of daily new cases increased by nearly 70%, to more than 26,000; hospitalizations have jumped by more than one-third, according to the Centers for Disease Control and Prevention.

Part of the reason is that less than half of the U.S. population is fully vaccinated. Some scientists and physicians worry vaccine hesitancy is fueled by the fact that shots available in the United States—made by Pfizer and BioNTech, Moderna, and Johnson & Johnson (J&J)—have been authorized on an emergency basis but have yet to be fully approved. Antivaccine activists, talk show hosts, and far-right politicians have made the vaccines’ “experimental” nature a talking point.

Full approval from the Food and Drug Administration (FDA) could help win over skeptics, says Monica Gandhi, an infectious disease physician at the University of California, San Diego. “It means something to people for it to be approved,” she says. “It just seems like the simplest, easiest thing we could be doing right now.”

Pfizer and Moderna have both applied for full FDA approval for their jabs, but it could be months away. Here’s where things stand.

Why haven’t the vaccines available in the United States been approved yet?

All three vaccines have been given an emergency use authorization (EUA), which FDA offers during crises as a quick way to give people access to potentially lifesaving medicines. In the past, EUAs have typically been used for drugs during “very catastrophic, immediate circumstances, like an anthrax attack,” says Jesse Goodman, a former chief scientist at FDA who’s now at Georgetown University. The COVID-19 pandemic marks the first time EUAs have been granted for new vaccines.  

To receive an EUA, vaccine manufacturers had to follow a special set of guidelines that asked for safety and efficacy data from clinical trials involving tens of thousands of participants, as well as information on vaccines’ quality and consistency. Pfizer and Moderna both received an EUA in December 2020; J&J’s came in February. Based on the real-world data they have collected since then, Pfizer applied to FDA for full approval in early May, and Moderna on 1 June. J&J is expected to follow soon.

What’s the difference between full approval and an EUA?

It’s one of scale. FDA will review much more data, covering a longer period of time, before granting full approval. “It’s not a huge difference, but it is a real difference,” Goodman says. The agency will analyze additional clinical trial data and consider real-world data on effectiveness and safety. It will inspect manufacturing facilities and make sure quality control is very strict. “It’s an exhaustive review,” Goodman says.

FDA is already familiar with much of the data, however, for instance on the very rare side effects caused by the J&J and Pfizer vaccines that didn’t show up in clinical trials.

When might the vaccines be approved?

On 16 July, FDA accepted Pfizer’s application “under priority review”—meaning it will move faster than during standard reviews, which typically take at least 10 months; the agency now has until January 2022 to review the materials. That seems like a long time, but last week an FDA official told CNN that the decision is likely to come within 2 months. “The review … has been ongoing, is among the highest priorities of the agency, and the agency intends to complete the review far in advance of the [January] Date,” an FDA press officer confirmed to Science in a statement.

FDA has not formally accepted Moderna’s application, possibly because the company has not yet submitted all the required materials.

Why have there been calls for faster approval?

Full approval could help overcome vaccine hesitancy, Eric Topol, director of the Scripps Research Translational Institute, wrote in a recent op-ed in The New York Times. “Some people who understand that the ‘E’ in ‘EUA’ stands for ‘emergency’ are waiting for full FDA approval before they receive a shot,” he wrote.

“I think it’s fair to say that any number of us who are clinical infectious disease doctors and in public health are frankly a little surprised at how long the process is taking,” says William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center.

“I want [FDA] to be careful. I also want them to move it along,” Schaffner says. “Frankly, I’d like them to work on the weekends. The people who are vaccinating are working on the weekends. The virus is working on the weekends.”

Will approval really convince more people to get vaccinated?

About 30% of unvaccinated people say they were waiting for vaccines to receive full approval, according to a survey of 1888 adults conducted in June by the Kaiser Family Foundation. But the report cautions that for many people, FDA approval is likely “a proxy for general safety concerns.” Not everyone now focused on approval may actually get a vaccine, especially if they perceive the approval process as rushed or politically motivated.

“For the people who are really dead set against getting the vaccine at this point, I don’t know that the FDA giving it full approval is going to make a huge difference,” says Krutika Kuppalli, an infectious disease doctor at the Medical University of South Carolina who says many of her patients are wary of COVID-19 shots.

But full approval may sway some people. For example, for members of groups that have been treated poorly by the health care system, signing a consent form to get vaccinated—a requirement for vaccines with an EUA—may be a psychological barrier, Gandhi says: “Signing a consent that says ‘experimental’ and the phrase ‘experimental’ brings up issues of experimentation on Black and brown communities.”

Will approval pave the way for mandatory vaccinations?

More than 500 U.S. universities and some high-profile hospitals have already issued vaccine mandates, meaning staff and students must be vaccinated.

But many schools and hospitals are hesitant to ask their employees to take what is technically still an experimental product and are holding out for full approval; so is the U.S. military. Some states, including those with some of the lowest vaccination rates in the country, such as Alabama, Arkansas, and Tennessee, have gone so far as to ban mandates in schools and colleges until vaccines are fully approved. (Conversely, a judge this week upheld Indiana University’s vaccine mandate after it was challenged by a group of eight students.) Once a vaccine is approved, “I think it will be on firmer foundation for organizations and businesses to mandate it,” Goodman says.

In France—where vaccine hesitancy is also running high—more than 1 million people signed up for a vaccine after President Emmanuel Macron announced on 12 July that vaccination would become mandatory for health care workers and “health passes” would be required to enter malls, bars, restaurants, and other public places. But those measures proved controversial as well: Tens of thousands took to French streets on Saturday in protest.

Could FDA speed up its approval process?

Perhaps, but the agency does not want to rush. “Any vaccine approval without completion of the high-quality review and evaluation that Americans expect the agency to perform would undermine the F.D.A.’s statutory responsibilities, affect public trust in the agency and do little to help combat vaccine hesitancy,” FDA’s Peter Marks wrote in The New York Times in response to Topol’s plea for speed.

“Any claims that this is taking a long time [are] almost like saying you don’t want FDA to do the normal, complete job that it does,” Goodman says. Regulatory rigor is especially important for messenger RNA vaccines, which use an entirely new technology, he adds.

Is it safe to get a vaccine that only has an emergency approval, not full approval?

Every expert Science talked to had the same message: The data amassed so far show the vaccines given an EUA in the United States are very safe and very effective. “It was really incredible to see how well these vaccines worked in the clinical trials,” Gandhi says.

“The vaccines are such a gift,” says Cody Meissner, a pediatrician at Tufts Children’s Hospital specializing in infectious diseases and a member of FDA’s vaccine advisory committee. “Every adult should get this vaccine.”