This Oct. 14, 2015 file photo shows the Food & Drug Administration campus in Silver Spring, Md. Credit: Andrew Harnik / AP

WASHINGTON — A surge in COVID-19 cases across the U.S. brought on by the fast-spreading delta variant is increasing pressure on U.S. drug regulators to fully approve Pfizer Inc.’s vaccine, the first one to apply for full licensure in the U.S.

Full approval could help the Biden administration ramp back up its immunization drive and reassure vaccine holdouts that the shots are safe. It could also make it easier for more schools and workplaces to put immunization mandates in place.

Meanwhile, breakthrough cases that penetrate the shot’s defenses are being monitored by health officials. While the Pfizer-BioNTech SE messenger RNA-based vaccine, cleared in the U.S. via an emergency-use authorization late last year, remains highly effective at preventing severe disease, the question of whether booster shots will be needed looms as fall approaches.

Bloomberg News spoke with Peter Marks, the head of the FDA division that is reviewing Pfizer’s approval application, about that process and other vaccine topics, including how the agency will decide whether booster shots are needed. The questions and answers have been edited for clarity and length.

Q. President Biden said recently that he expects a decision on full approval of the Covid-19 vaccines, such as the Pfizer vaccine, by September or October. Is this a timeline you will meet?

A. I’m hoping we’re not going to disappoint the president. Everyone here understands the need to do this with the same care and rigor that we always do, and also with speed and urgency, given that we’re in the middle of a global pandemic.

Q. There’s a perception that the FDA has dragged its feet on granting the Pfizer vaccine full approval. Can you explain what extra steps are involved?

A. The original emergency-use authorization was based on two months of median follow-up data. Now we have six months of follow-up data, and all the manufacturing information we normally need for full licensure. Going over an order of magnitude more data, inspecting the facilities, and doing all of the things that we normally do takes a little bit of time. The last thing I want is anyone who is vaccine-hesitant to be able to say, now it’s approved, but it wasn’t the same kind of approval, so I’m still not going to get vaccinated.

Q. How focused is the FDA on rare cases of heart inflammation associated with mRNA vaccines?

A. Myocarditis is clearly one of the emerging serious adverse events that we have to keep track of. We are looking at this quite closely using a variety of different systems. To date, the benefits have clearly outweighed the risks of this vaccine. We’ll want to describe those risks as best as possible. So we need to have the benefits locked down and we have to have the risks locked down. That’s what we’re working through now.

Q. Why did you decide now to accelerate the review process?

A. Back at the end of June, we were all getting ready to do a happy dance. We are now in the middle of a very real fourth wave. People are contracting this disease and dying of it at increasing numbers again, particularly in regions that don’t have high vaccination rates. There are a population of people who say that if there were an approved vaccine, they would be more likely to take it. So we view this as an opportunity to help save lives.

Q. The Biden administration has indicated it’s not only going to consider company data to decide whether booster shots are needed. Can you tell us what additional data the FDA is looking at?

A. There are two separate things with third shots. There are third shots for immunocompromised people. That’s a smaller group, a few percent at most. Those people don’t make a good primary immune response up front. They may need a third dose just a few weeks after their second dose. Then there’s the booster issue for the general population. There, we will look at the data that the companies have, but we’ll also look at the data coming out of countries like Israel, data coming out of studies in the United States, and real-world evidence that we get our hands on from other countries. Any data that would help understand when immunity tends to wane will be brought to bear.

Q. When do you expect to get this data?

A. We’re talking about over the next one to two months. We have to get on top of this pretty soon, because we’ll have to make some decisions here.

Q. Is there any minimum amount that efficacy would have to wane before the FDA authorizes booster shots?

A. We don’t have some predetermined minimum. We’re going to look at the totality of the evidence. That includes understanding what the implications are here of having waning immunity at the same time we have a variant that’s more transmissible, like the delta variant. We need to think of what will ultimately best protect against continued cycles of this virus.

Q. How much longer is the FDA going to be releasing COVID vaccines via the emergency authorization process?

A. There probably is going to be a point at which we stop giving emergency use authorizations, but right now one wouldn’t want to rule out continuing to give emergency-use authorization. We still don’t have an approved protein-based vaccine, for instance, and there are some people where that might be a very good alternative.

Q. Do you think it is likely during the coming school year a vaccine will be authorized for all school-aged children?

A. Anything’s possible, but we’re likely more likely to see something for the five- to 11-year-olds sooner than the youngest children. Preschool age children may be a little bit later because of the way the studies are being done.

Q. Why did the FDA decide to ask drugmakers to expand the size of the vaccine trials in kids under 12?

A. The size is about three to four times what they originally were. The idea was to try to have a larger safety dataset, to be able to understand if there were any more side effects that might be there. We want people to feel really confident in what comes out.

Q. Anything you want to add?

A. Everything we are doing here is focused with the idea that it’s not a vaccine that ends a pandemic. It’s vaccination. We have to make sure that when we’re done with our processes, that people have trust in them.

Story by Robert Langreth, Bloomberg News.