Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention recommended booster shots of Pfizer-BioNTech’s COVID-19 vaccine for people over age 65 and those who might be more at-risk of infection and COVID-19, including people with underlying medical conditions and who work in health care, schools and other settings where they are at higher risk of exposure to the COVID-19 virus. Walensky’s recommendation, issued late on Sept. 23, deviated slightly from the advice of the CDC’s Advisory Committee for Immunization Practices (ACIP) that came hours earlier.
In a four-part vote, the ACIP recommended booster shots of Pfizer-BioNTech’s COVID-19 vaccine for people 65 years or older, as well as anyone over 50 with certain underlying medical conditions. The committee backed away from full recommendation of a booster for people 18- to 49-years-old with underlying medical conditions, saying that they may receive a booster if they desired, based on individualized decisions about the benefits and risks to them.
In the last of its four votes, the committee decided against recommending booster shots for adults working in high-risk settings such as health care and school systems. That vote went against the Food and Drug Administration’s (FDA) decision on Sept. 22 to authorize a booster dose of the Pfizer-BioNTech vaccine for people over 65-years-old, those ages 18 to 64 who are at higher risk of getting the disease, such as people with health conditions that weaken their immune systems, as well as health-care, front-line and emergency workers and teachers among others whose jobs make them more vulnerable to getting exposed to COVID-19. The FDA recommended that the booster be given at least six months after an individual receives the second of the two-dose vaccine to all of those groups.
In the final CDC recommendation, Walensky backed the FDA and is recommending that people who work in high risk settings, including health care, front line and essential workers such as teachers, be allowed to chose if they would like to get a booster dose to mitigate their risk, similar to people 18- to 49- years old with underlying medical conditions. “I believe we can best serve the nation’s public health needs by providing booster doses for the elderly, those in long-term care facilities, people with underlying medical conditions, and for adults at high risk of disease from occupational and institutional exposures to COVID-19,” Walensky said in a statement announcing her decision. “This aligns with the FDA’s booster authorization and makes these groups eligible for a booster shot.”
While the CDC’s ACIP often follows the recommendation of the FDA, it doesn’t have to—the CDC’s mandate, which focuses more on public health goals, differs slightly from that of the FDA, which is more centered around evaluating safety and efficacy. “What we need to be doing is to look at the totality of evidence and think about what makes the most sense using the tools we have to protect as many people as possible, and how to operationalize this considering other things like feasibility,” Dr. Beth Bell, professor of global health at the University of Washington, reminded the committee. While the members generally agreed about recommending a booster for those over 65, they were divided about the necessity of the booster at this time for younger people, even those at higher risk of COVID-19 exposure because of their jobs or other circumstances.
So far in the U.S., 220 million doses of Pfizer-BioNTech have been administered, and 27 million people over age 65 years have received both doses of the vaccine. They were among the first to get vaccinated after Pfizer-BioNTech’s vaccine was approved, and now show the first signs of waning immunity—which is why the committee prioritized them to receive a booster dose to strengthen that protection.
In discussing whether boosters should also be extended to people with underlying medical conditions and those whose jobs might put them at higher risk of exposure, members were divided over how strong the data are concerning the risk of severe disease in this group. Some members noted that authorizing the booster for these populations would raise concerns about health care equity, arguing that it could deepen gaps in coverage as those without access to care who remain unvaccinated continue to miss out on the opportunity to get protected against COVID-19. Ultimately, the committee decided to fully recommend the booster for everyone over 50 with underlying medical conditions, but to offer a less full-throated endorsement for those aged 18 to 49 with such conditions. For them, the ACIP is recommending that people choose for themselves whether they want to get a booster dose.
The CDC committee then deviated from the FDA when it came to people like health care workers under age 65 whose jobs might put them at increased risk of exposure and infection, noting that there isn’t strong evidence to suggest that they, if they are vaccinated, are experiencing higher rates of severe disease. The data show that the currently approved two doses of Pfizer-BioNTech continue to provide good protection against COVID-19, especially against severe illness, hospitalization and death. In particular, while Pfizer-BioNTech did provide the FDA and CDC with some data showing that a booster shot raised antibody levels among young people, those data only followed those people for a few months. And committee members also raised the point that, while apparently rare, some young males can develop a rare inflammation of the heart tissue as a side effect of getting the vaccine.
That’s why some of the members emphasized that their support of the booster was an interim one, for an initial group of people, based on the available data available. “This is the beginning of a lot of activity around booster doses,” said Bell. “At this moment, given the lack of evidence for marginal benefit of boosters in people in certain groups who have received the Pfizer-BioNTech primary series—it’s too narrow, and too soon, and given the potential risks or adverse outcomes it’s worth waiting until we know a little more about what we are doing, and we can better assess the opportunity costs, and the unintended consequences.”
The CDC committee was instructed that its booster decision would only apply to those who had been inoculated with the Pfizer-BioNTech vaccine to begin with, since the FDA only reviewed data on that population. Some committee members, however, argued that the decision should also apply to people who initially got Moderna or Johnson&Johnson-Janssen shots in order to be fair and equitable. (Moderna has also submitted a request to the FDA for authorization of a booster dose of its vaccine, but the agency has not yet reviewed those results.) Such mixing and matching of doses, however, isn’t supported by currently available data.
Some committee members, like Dr. Nirav Shah, director of the Maine Center for Disease Control and Prevention, argued that allowing mixing and matching of boosters would help more people to get vaccinated. He noted the burden of asking people to keep track of their vaccination records, and of asking those administering vaccines to validate those records. Dr. Sarah Long, professor of pediatrics at Drexel University College of Medicine, added that limiting the booster to only those who initially got the Pfizer shot would be especially unfair to those living in long-term-care facilities who received an initial series of Moderna vaccine and would not be able to get a booster while their neighbors who received the Pfizer shot would be vaccinated again. “I don’t understand how later this afternoon we will say to people over 65 years that you are at risk of severe disease and death, but only half of you can protect yourselves right now,” she said.
But, as Dr. Doran Fink, from the FDA’s office of vaccines research and review told the committee, “there is currently no data available to inform interchangeability of authorized COVID vaccines, either for completing of the [two-dose] primary series or for use as a booster dose.” Because of this lack of data, the CDC panel ultimately decided that only people who previously received two doses of the Pfizer-BioNTech vaccine should receive a booster dose of the Pfizer-BioNTech shot. This, however, is another area where today’s recommendation may not be the final word: study results on such mix-and-match approaches are expected imminently; researchers said the trial was completed, and the data have been submitted to a journal for publication.
The committee stressed that, for most people who have been vaccinated, the current two-dose regimen still provides strong protection against SARS-CoV-2, including against the Delta variant. “Our decision today is not about who deserves a booster but who needs a booster,” said Dr. Matthew Daley, senior investigator at Kaiser Permanente Colorado. “If you are in a group for whom a booster isn’t recommended today, the reason the booster isn’t recommended for you today is because the vaccine efficacy against serious outcomes is already high for those who have gotten the primary series.”
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