The Food and Drug Administration on Friday issued an emergency authorization for a Covid-19 vaccine developed by Pfizer and its German partner, BioNTech, a seminal moment in the effort to curb a pandemic that has so far infected an estimated 16 million people and killed nearly 300,000 in the United States.
The decision means vaccinations will begin in a matter of days in individuals 16 years of age or older, though the FDA said the vaccine should not be given to individuals with a history of severe allergic reaction to any component. Such reactions were reported once vaccinations began outside of clinical trials in other countries. Initial supplies of the two-dose vaccine are expected to be used primarily in two groups most at risk of getting infected or developing severe disease: health care providers and residents and staff of long-term care facilities.
“While not an FDA approval, today’s emergency use authorization of the Pfizer-BioNTech COVID-19 Vaccine holds the promise to alter the course of this pandemic in the United States,” said Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, in a statement.
The vaccine is the first to be authorized in the United States, and has already been authorized in the United Kingdom, Canada, and several other countries. But neither in those countries, nor in the United States, is the vaccine expected to be a panacea for the pandemic.
While the vaccine was shown to reduce the risk of developing symptomatic Covid-19 infection by about 95% in Phase 3 clinical trials, a number of factors may constrain its potential to turn the pandemic’s tide, at least in the short term. Among other issues: Initial supplies of the vaccine are extremely limited; many Americans are reluctant to take the vaccine at all; and in certain populations, including people who are pregnant and children, the vaccine has not yet been tested. The FDA noted in a fact sheet for health care providers about the vaccine that there aren’t enough data yet to inform whether there are vaccine-associated risks specific to pregnancy or lactation.
Importantly, while the vaccine reduces the risk of developing symptomatic infection, it’s not yet clear whether it also reduces transmission of the virus that causes the disease, SARS-CoV-2. It’s possible that people who are vaccinated can still contract the virus and then transmit it to others, though they themselves would not get sick. As a result, health officials are urging everyone, including the vaccinated, to continue to practice social distancing measures and to wear masks.
The Pfizer/BioNTech vaccine was developed at breakneck speed, and the Trump administration agreed over the summer to an initial $1.95 billion purchase of 100 million doses, before knowing whether it would be safe and effective.
In clinical trials, it proved to be both. The most common side effects included pain at the injection site, fatigue, and fever. Serious adverse reactions were rare. In a 44,000-volunteer study, there were four cases of Bell’s palsy, a temporary weakness or paralysis, in the vaccine arm and none in the placebo arm. There were also 64 cases of lymphadenopathy, a swelling of the lymph nodes, in the vaccine group versus six in the placebo group. Those cases all resolved.
In a press conference Saturday, Marks emphasized that the FDA will continue to monitor the prevalence of severe allergic reactions associated with the Pfizer vaccine, and that it may need to revise its warnings moving forward. He added, however, that the agency feels comfortable barring only those with a history of severe reactions to an ingredient in the vaccine, as opposed to barring all Americans with a history of any severe allergic reaction.
“It turns out about 1.6% of the population has had a severe allergic reaction of some sort or another to a food or some environmental aspect and we would really not like to have that many people not be able to receive the vaccine, so we looked very closely at the databases, and we feel comfortable that we’re telling people that unless they’ve had a severe allergic reaction to the vaccine, or one of its components they can receive it,” Marks said. “We may have to modify things as we move forward, but for right now we’re comfortable with this.”
The FDA’s decision came one day after an advisory committee recommended that an emergency use authorization be granted to the vaccine.
“We worked quickly based on the urgency of this pandemic, not because of any other external pressure,” FDA Commissioner Stephen Hahn said in a briefing Saturday.
The same committee that recommended authorization is scheduled to meet on Dec. 17 to review data on a vaccine developed by Moderna, a biotechnology company based in Massachusetts. Its vaccine had efficacy levels similar to Pfizer’s and is based on the same technology, known as messenger RNA. It is widely expected to be authorized.
Operation Warp Speed, the U.S. effort to fast-track development of Covid-19 vaccines, currently estimates it will have enough vaccine for 20 million people by the end of December between the Pfizer and Moderna vaccines.
A number of other vaccine candidates are still in clinical trials.
The rollout of any vaccine is expected to be complex, and there remain concerns about vaccine makers’ ability to scale up manufacturing to meet demand, not just in the United States but globally. Still, the development and distribution of a vaccine less than a year after the emergence of an unknown pathogen is widely considered a feat once thought impossible.
This story has been updated with additional information from the FDA.