(CNN) Vaccine advisers to the US Centers for Disease Control and Prevention argued long and hard Thursday before endorsing giving booster doses of Pfizer's Covid-19 vaccine to people 65 and older, long-term care facility residents and certain people with underlying conditions.
However, the advisers voted against recommending a booster dose for people whose jobs or situations put them at high risk of vaccine breakthrough infection -- rejecting part of the US Food and Drug Administration's emergency use authorization.
The FDA on Wednesday had authorized giving boosters to people 65 and older and those at higher risk of severe disease and death, as well as people such as health care workers at higher risk of breakthrough infections because of their work.
But the broad nature of the EUA did not sit well with several members of the CDC's Advisory Committee on Immunization Practices, who met Thursday to decide how best to implement the FDA's authorization.
The CDC advisers voted unanimously to recommend a single Pfizer/BioNtech Covid-19 vaccine booster to people 65 or older and long-term care facility residents at least six months after they were fully vaccinated.
They also voted easily to recommend boosters to people 50 and older with underlying medical conditions that might put them at higher risk of severe disease.
Such people might include patients with cancer, stroke, chronic kidney disease, chronic obstructive pulmonary disease or COPD, diabetes, heart conditions, obesity, as well as pregnant women and smokers, the CDC's Dr. Kathleen Dooling told the meeting.
However, the advisers were divided on the question of recommending such boosters to people under 50. In a separate question, they voted 9-6 to recommend boosters to people 18-49 who have underlying health conditions.
After long arguments, they voted against recommending boosters for people whose occupations put them at high risk of infection. It was a rare break with the FDA's advice.
"We may just as well say give it to everyone 18 and older," said Dr. Pablo Sanchez, a professor of pediatrics at Ohio State University.
"I feel very uncomfortable about this," said Dr. Wilbur Chen, a professor of medicine at the University of Maryland School of Medicine. "The implementation part of this is going to be fraught with such complexity that the people with the best health literacy will get boosters."
But ACIP chair Dr. Grace Lee, a Stanford University pediatrician, said her personal experience made her aware of the need to make boosters widely available.
"I have cared for children who have died of Covid," she said. "Their family members wish that they had extra protection for their kids."
Earlier in the day, a CDC analysis showed it was much more beneficial to give a booster dose to people 65 and older than to people in younger age groups.
Immunizing 1 million people 65 and older would prevent 8,000 cases of Covid-19 and 2,080 hospitalizations over six months, the CDC's Dr. Megan Wallace told the meeting. The biggest risk from vaccination with Pfizer's vaccine is a rare heart inflammatory condition called myocarditis -- and just one case of myocarditis could be expected in a million people vaccinated in that age group, Wallace said.
"Even if myocarditis risk doubles -- we still see more hospitalizations prevented than myocarditis cases expected," Wallace said. For every 1 million booster doses given, the model projected four cases of myocarditis among females and 48 among males aged 18 to 29.
A booster would prevent 9,500 cases and 114 hospitalizations among 1 million people 18-29 over six months, Wallace told the meeting.
To put it another way, she said, to prevent one hospitalization over six months, doctors would need to vaccinate 8,738 people 18-29; 3,361 people 30-49; 2,051 people 50 to 64 and just 481 people 65 and older.
While they voted easily to recommend boosters for the older age groups, members of the committee worried that they were sending the wrong message.
"I worry we're getting distracted by the question of boosters and Pfizer when we have bigger and more important things to do in the pandemic," Dr. Helen Keipp Talbot, an associate professor of medicine at Vanderbilt University, told the meeting.
"And along those lines -- we're fighting a pandemic and it's not because people got two doses of vaccine. It's because people are unvaccinated," she added.
"And I really feel like yes we may move the needle a little bit by giving a booster dose," Talbot said in comments given before ACIP voted on the question. "But the real fact of the matter is this is a pandemic of the unvaccinated," she said.
"I feel like we are putting lipstick on frogs....This is not going to solve the pandemic."
Dr. James Loehr of Cayuga Family Medicine in Ithaca, New York said he did not think adding boosters would save that many lives.
"I feel the goal is to decrease hospitalizations, and overall I think that the vaccinations will decrease hospitalizations, but I also feel that we're getting too much ahead of ourselves and that we have too much hope on the line with these boosters," he said.
"Even if we gave boosters to all 13 million people over 65 who have had the Pfizer vaccine in the past, that might be about 200 fewer hospitalizations a day, which is a lot," he added. But the bigger goal, he said should, be keeping the unvaccinated, especially children, out of the hospital.
"However, having said that, we shouldn't let the perfect be in the way of the good. And if we can do a little bit of good by giving boosters to people over 65 I'm in favor of that," Loehr said.
After CDC Director Dr. Rochelle Walensky signs off on the ACIP recommendations, booster shots may be given immediately to those for whom they are recommended.
The CDC's Dr. Amanda Cohn, executive secretary for ACIP, said the committee can come back any time in the future to adjust their recommendations. "We ave several meetings ahead of us," she said.
Third doses are already approved and recommended for some people who are immunocompromised and at high risk of severe disease from Covid-19.
The FDA's EUA only covered Pfizer's vaccine, with boosters going to those who got their first two doses of Pfizer/BioNtech vaccine at least six months ago. The FDA has not decided on Moderna's application for booster authorization, and Johnson & Johnson has not yet applied.
Dr. Peter Marks, who heads the FDA's vaccine branch, the Center for Biologics Evaluation and Research, said there is no precise timeline yet for those vaccines.
"I think we understand at FDA the relative urgency here of trying to have a solution for anyone who's been vaccinated with any of the authorized or approved vaccines," Marks told the meeting.
"I can tell you that we will proceed with all due urgency to try to get there as rapidly as possible working with the various vaccine sponsors."