CNN  — 

Vaccine advisers to the US Food and Drug Administration voted Friday to recommend emergency use authorization of a booster dose of Pfizer’s vaccine to people 65 and older and those at high risk of severe Covid-19 six months after they get their first two shots.

But the FDA’s Vaccines and Related Biological Products Advisory Committee rejected a broader application to approve booster doses of Pfizer’s vaccines for everyone 16 and older six months after they are fully vaccinated.

Members of the committee expressed doubts about the safety of a booster dose in younger adults and teens, and complained about the lack of data about the safety and long term efficacy of a booster dose.

Biden administration officials had previously announced a plan to begin administering booster doses to the general population during the week of September 20, irritating some members of the committee. They later noted that any action would be pending signoff from the FDA and US Centers for Disease Control.

Some of the advisers – a group of vaccine experts, immunologists, pediatricians, infectious disease specialists and public health experts – have said the process was rushed, and several members said during the meeting they wanted to see more data.

The group unanimously supported authorization for the more limited higher-risk group, and they informally advised the FDA to include health care workers or others at high risk of Covid-19 exposure in the EUA, too. The FDA will now craft its decision on Pfizer’s request, taking into account the committee’s guidance.

Dr. Archana Chatterjee, dean of the Chicago Medical School at Rosalind Franklin University, noted the lively discussion and adjustments during the meeting proved they are truly independent advisers.

“I think this should demonstrate to the public that the members of this committee are independent of the FDA, and that in fact we do bring our voices to the table when we are asked to serve on this committee,” she said.

Pfizer’s case for boosters

During the meeting, Dr. William Gruber, senior vice president of vaccine clinical research and development at Pfizer, said several studies indicate that people’s immunity can and does wane and that giving booster doses restores that immunity – sometimes to levels higher than seen at initial vaccination. He said people who got the boosters did not have any more side effects than seen after the first two doses.

And Gruber said while the two-dose Pfizer vaccine continues to protect well against severe infection, hospitalizations and deaths, there are hints that could change.

The company relied heavily on data from Israel, where vaccinated people started to get breakthrough infections. Israeli researchers earlier told the meeting that adding booster shots in Israel helped keep many people out of the hospital.

“The Israeli experience could portend the US Covid-19 future,” Gruber said. “Israel and the United States real world evidence suggests that vaccine efficacy against Covid-19 infection wanes approximately six to eight months following the second dose,” he added.