With many Americans still unvaccinated and the delta variant sparking a sharp rise in coronavirus cases, the Food and Drug Administration is under growing pressure to grant full approval to coronavirus vaccines being used under the agency’s emergency authority.

Some lawmakers and health care experts pushing for quick approvals note that the shots – particularly the highly effective mRNA vaccines by Pfizer-BioNTech and Moderna – have been administered to tens of millions of people in the United States and worldwide without significant problems. They argue that universities, governments and employers would feel more comfortable imposing vaccine mandates after full approvals, and predict some people would be more willing to get the shots.

Pfizer and BioNTech submitted their request for full approval, called a biologics license application, on May 7, and Moderna began a rolling submission in June. Johnson & Johnson has said it will submit its application later this year. Typically, it takes the agency at least several months to grant a full approval for a vaccine. But some officials have said that the Pfizer vaccine could be approved by late summer or early fall.

In an interview Friday, Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, which regulates vaccines, said the agency is pursuing “an all hands-on-deck” strategy to accelerate an already expedited effort to grant full approval to the Pfizer-BioNTech vaccine. He said the agency was essentially “in a sprint” to complete the process.

He also discussed the differences between emergency use authorizations, which are temporary clearances for public health emergencies, and full approvals, which remain in effect indefinitely unless a problem with a vaccine emerges.

• When do you think the FDA will give the Pfizer vaccine full approval?

I can’t speak to a date when we intend to have this done. But what I can say is we are going to move with all due diligence to get the review done with our usual high quality, as rapidly as we can. We know how important it is for people to be able to get vaccinated. We know that there are students going back to college who would like to see a licensed vaccine before they get vaccinated. And we understand that, and we will work toward getting this across the finish line as rapidly as possible.

• What are some of the differences between what’s required for an emergency use authorization compared to a full approval?

The emergency use authorization [for Pfizer] was based on [clinical trial] data of 21,700 or so vaccinated individuals with a mean follow-up of two months, and there were another 21,700 who got the placebo. Now a fair number of people [who got the placebo] have crossed over and received the vaccine, and the follow-up for everyone is at least six months. You have a lot more data to review than for an emergency use authorization. In terms of pages to review the change is an order of magnitude. It’s going from tens of thousands of pages, to hundreds of thousands of pages.

Additionally, the manufacturing for a full approval has to be much more well-described and detailed than it is for an emergency use authorization. Plus, we have to do additional inspections of facilities and I can say that for Pfizer, there are lots of facilities involved in different countries, so there’s a lot of things to tie up in order to put a ribbon around this package. Because, at the end of the day, when we put this forward as a licensed product, we don’t want someone to say, “Well, they didn’t come and inspect this time and, by the way, there is something wrong here.”

• But don’t we already have information on tens of millions of people who have gotten the vaccine?

The idea is to have at least six months’ follow-up on those who received the vaccine [in the clinical trial] – that’s at least what we normally do for biologic license applications.

Some people say, “Well, look, we vaccinated millions of people and why can’t you just use that?” Well, we don’t follow all those millions of people in the same manner that we are able to follow people who are enrolled in clinical trials.

For those individuals enrolled in trials who have had an adverse event, there is an adverse event report form and [clinical reviewers] go through these forms. The worst of the adverse events get reviewed at a second level in order to really understand what is going on. This means that when we eventually have a package insert for the vaccine and say there is a certain incidence of an adverse event, that is something we feel confident in.

It is much more challenging to get that kind of experience from the field in a highly accurate manner. Maybe someday we will have a wonderful, integrated single medical record throughout the entire United States where we can monitor everyone and we can just push a button and get those data. But we don’t have that now.

• What are some of the manufacturing issues the FDA is looking at?

The whole process has to work, there have to be appropriate controls and the testing that has to be done. It’s not just the vaccine drug substance, but also how that drug substance is made into drug product and put into the vials. The whole process is inspected, and then we have to make sure that the end product is truly ready to be released. There are a lot of different steps that the FDA has to review that go into all of this.

• Do you think a full approval will persuade unvaccinated people to get the shots?

You can be the skeptic and say, “Oh, c’mon, if you were going to get vaccinated, you were going to be vaccinated anyway, and that’s just the excuse of someone who is never going to get vaccinated.”

On the other hand, after seeing all the emails from very respectable people – providers, politicians, tribal chiefs – there are any number of people who are saying that they are really uncomfortable with an experimental vaccine. This EUA thing sounds really weird to them. They want an FDA-approved product. Whether they will show you the money and get vaccinated afterwards or not, I believe that at least some of them will.

• Does a full approval make it make it easier for employers and governments to require vaccines?

I’m speaking in an informal sense, not like a [Department of Justice] lawyer … But by and large, there seems to be a better feeling for having a licensed product to make something a requirement.

• How long does a typical vaccine review take?

While each vaccine review is unique, the FDA aims to complete priority vaccine reviews within eight months of receiving an application for approval and standard reviews within 12 months of receipt.

• Under an emergency use authorization, doctors must use the vaccines exactly as directed by the FDA. But once the vaccine is approved, can doctors use it off-label? Could they give third shots to patients even if the FDA has not specifically cleared that?

An emergency use authorization is made with conditions for use and that is because the data usually are for specific circumstances and we don’t have a lot of that data. So we say to the doctor, “Use this the way we tell you to use it, as in our letter of authorization.” There is not such a thing as off-label use.

On the other hand, once you have a licensed product, if a provider wants to use it in a responsible way, according to the practice of medicine, then that is their right and they can use it off label. They could use it as they see fit, but they would actually have to feel like they were within the scope of practice of medicine in their jurisdiction … and doing something reasonable.

Like many of the vaccine actions during the COVID-19 pandemic, once the FDA finishes the important regulatory steps in approving a vaccine, the Advisory Committee on Immunization Practices [of the Centers for Disease Control and Prevention] will meet again to consider recommendations for health care providers on how best to deploy the vaccines to people.