The committee of independent vaccine experts voted 17 to 4, with one abstention, that the benefits of the vaccine from Pfizer Inc. and BioNTech SE outweigh the risks for use in people ages 16 and older. The FDA doesn’t have to follow the recommendation, though often it does agree with its advisers.

An authorization could come from the FDA within days. That would open the gates for shots to be distributed across the U.S., in a massive undertaking that will put health-care workers and long-term care facility residents at the front of the line, and mark a first step toward ending a pandemic that has killed some 290,000 people in the U.S.

Part of the panel’s discussion focused on whether there was enough data to support the vaccine’s use in 16 and 17 year olds, leaving some pediatricians on the advisory committee uncomfortable with voting in its favor. However, other members said data from older trial participants could be extrapolated to younger people.

Pfizer shares rose 2.4% in trading after the market close in New York. Germany-based BioNTech’s American depositary receipts gained 3%.

“We are pleased with the strong majority vote, and if the FDA issues an authorization, stand at the ready to bring this vaccine to people in the U.S. in an effort to help combat this devastating pandemic,” Pfizer Chief Executive Officer Albert Bourla said in a statement.

Clinical trial data submitted by the companies and confirmed by the FDA’s staff showed the vaccine was 95% effective and worked well regardless of age, gender, race, ethnicity or underlying conditions that cause people to be at high risk of severe COVID-19 symptoms.

There were eight virus cases within the group who received the shot and 162 in those who got a placebo, according to FDA staff. Pfizer enrolled almost 44,000 people in the trial.

Side effects of the shot were mild and developed more frequently in those age 55 and younger, with no signs of serious safety concerns based on two months of trial data, FDA staff found. After the second injection, fatigue and headache were among the most common reactions. The vaccine employs a technology called messenger RNA that’s never before been used in human vaccines.

States will make the final decisions about who gets inoculated first, though advisers to the Centers for Disease Control and Prevention have recommended health-care workers and long-term care facility residents be prioritized.

The U.K. approved Pfizer’s shot earlier this month, but said people with a significant history of allergies should not take it after two people suffered reactions. The FDA asked Pfizer to assess the reactions, including a severe form called anaphylaxis, as the shot is used in the U.S., Susan Wollersheim, a medical officer at the agency, said in a presentation to the panel. The agency is continuing to collect information and will monitor for reactions closely “as an important potential risk,” Wollersheim said.

Persistent Issue

Panel member Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, suggested Pfizer study use of the vaccine in people with serious allergies as it moves toward seeking full FDA approval if it does get emergency authorization.

“This issue is not going to die until we have better data,” he said.

The government is prepared with a safety monitoring system that will go into place the first day of the immunization campaign, said Nancy Messonnier, director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases. The CDC is considering working with the National Academies of Sciences, Engineering and Medicine to evaluate safety issues that may arise when the vaccine is in use in the general population, she said.

Pfizer didn’t see any severe allergic reactions in its clinical trial, though the company is aware of the U.K. reports, said William Gruber, senior vice president of vaccine clinical research and development. Pfizer provided the FDA two months of post-vaccination safety data on clinical trial participants and will provide six months of such data when it applies for full approval of the shot.

Gruber said the company will apply for full FDA approval in April. Until Pfizer receives full approval, the agency still considers the vaccine experimental and does not allow the company to market the product.

The FDA has asked vaccine makers to continue studies comparing those who get the vaccine to those who get a placebo even after an emergency authorization is given so companies can seek full FDA approval. The request may be difficult to fulfill as trial participants become eligible for vaccines and want the protection instead of remaining in the trial.

Marion Gruber (no relation to Pfizer’s William Gruber), head of the FDA’s Office of Vaccines Research and Review, said the agency is open to other approaches to gathering more data on the vaccine to support full FDA approval.

There isn’t enough data on children younger than 16 to determine whether it will work in pediatric populations, FDA staff said. Data is also insufficient to make any determinations about pregnant, lactating or immuno-compromised people.

Pfizer’s Gruber said the company plans to submit data on 12- to 15-year-olds when it applies for full approval. Doran Fink, deputy director of the FDA’s clinical division of vaccines and related products applications, told agency advisers the agency expects development and toxicity data on use of the vaccine in pregnant animals later this month.

Those who do get vaccinated will still need to wear masks and practice social distancing to prevent spreading the disease. FDA staff said the shot prevents symptoms of COVID-19 but may not be as good at preventing infections that don’t show symptoms, meaning significant transmission would still be possible without basic health measures.

“We really as of right now do not have any evidence that it will have an impact on social life, on the epidemic,” said Patrick Moore, a panel member and head of the Cancer Virology Program at the University of Pittsburgh Cancer Institute.

The CDC will conduct observational studies as the vaccine is rolled out to the public to attempt to determine its effect on transmission, said Arnold Monto, chair of the panel, and an epidemiology professor at the University of Michigan School of Public Health.

‘Dramatic Success’

If the vaccine is cleared by the FDA, Gustave Perna, the general leading the vaccine rollout, said people would begin to get shots within 96 hours, though Health and Human Services Secretary Alex Azar has said it could occur within 24 hours. Between Pfizer and Moderna’s vaccines, a maximum of 20 million people in the U.S. are expected to have received one shot in the two-dose regimen by the end of the year.

The editors of the New England Journal of Medicine, which published the pivotal study of the vaccine Thursday, called the results a triumph that are impressive enough to hold up to any conceivable review.

“What appears to be a dramatic success for vaccination holds the promise of saving uncounted lives and giving us a pathway out of what has been a global disaster,” wrote Eric Rubin, editor-in-chief of the journal, and Dan Longo, the deputy editor.