CDC advisers recommend who can get booster shots of Pfizer's COVID-19 vaccine

Update: The CDC director made some changes in the final recommendations. Read the latest story here. Our earlier coverage is below.

A panel of the Centers for Disease Control and Prevention's outside vaccine experts voted Thursday to allow use of booster shots for many adults first vaccinated with Pfizer's COVID-19 vaccine at least six months ago, including those 65 and over and others at higher risk of severe COVID-19, clearing one of the last regulatory hurdles for third doses to be given this week. 

Booster shots of the vaccine, which goes by the brand name Comirnaty, could be available by the end of the day, after CDC Director Rochelle Walensky formally adopts the group's recommendations. The guidance passed by a majority vote on Thursday afternoon following a two-day meeting of the CDC's Advisory Committee on Immunization Practices. 

"I appreciate your meticulous review of the data available from CDC's own cohort studies, from FDA's review of Pfizer's studies, and from public health partners and institutions around the world," CDC Director Rochelle Walensky told the group as it began its meeting Thursday afternoon. 

"These data are not perfect, yet collectively they form a picture for us, and they are what we have in this moment, to make a decision about the next stage in this pandemic," added Walensky.

The ACIP's recommendations follow the authorization granted by the Food and Drug Administration for the shots late Wednesday, which narrowed eligibility from Pfizer's initial request for full approval of boosters in all Americans 16 years and older. 

Now people at least 65 years old or living in long-term care facilities, like nursing homes, will be eligible for booster shots. The advisers also voted in favor of a broader "permissive" recommendation for adult Pfizer recipients to receive a booster shot if they believed their individual benefits from the vaccine due to "underlying medical conditions" outweighed the risk of side effects. 

"I think in all reality that almost every American is at risk. We either are obese, or have a medical problem, or if we don't have high risk, we live with someone who's high risk, or we teach a group of kids that aren't eligible to get vaccine yet," said Vanderbilt University Professor Dr. Helen Keipp Talbot, a member of the ACIP.

"It may make more sense just to make it permissive for the U.S. population. And that way, patients can have conversations with their providers or their pharmacists to really kind of think through those risks," said Talbot.

A majority of the panel rejected a motion to include people at high risk of catching the virus due to where they live or work, which would have included health care providers or prisoners. The vote narrows eligibility for the shots from what the FDA first authorized, which had included all adults "whose frequent institutional or occupational exposure" put them at "high risk of serious complications" from COVID-19.

Eligibility for the boosters will be determined by "self-attestation," a CDC official told the panel, and people will not be required to provide documentation to prove they qualify. Local health officials on the panel voiced concern that implementing the recommendations could be "exceedingly challenging."

"Even though I certainly agree with the public health spirit underlying it from an implementation standpoint, this would result in the inevitable confusion and patchwork we saw back in January and February," said Dr. Nirav Shah, Maine's top health official and president of the Association of State and Territorial Health Officials.

Modeling presented by the CDC found the benefits of a booster shot to prevent hospitalizations likely outweighed the risks of rare side effects for most age groups, though acknowledging the benefits could decline as the current wave of cases subsides and was smallest among the youngest Americans.

"In this scenario of lower incidence, a lower pre-booster [vaccine effectiveness] is needed for the benefits of a booster dose to clearly outweigh the risks in males aged 18 to 29 years," said the CDC's Megan Wallace.

Two-thirds of vaccinated Americans are ready to get a booster shot, the CDC estimated citing unpublished survey data by the agency. Their polling found a third of the unvaccinated could be further discouraged to get vaccinated if booster shots were recommended, though officials later said that allowing booster shots would not mean Americans would need a third dose to be considered "fully vaccinated" by health authorities. 

"Based on our current data, the definition of fully vaccinated would remain the same after recommendations for a booster dose, the fully vaccinated, two weeks or more after completion of the primary series," the CDC's Dr. Sara Oliver told the panel. 

Under federal supply agreements, vaccinators are required to follow the panel's guidance on giving the shots. Until now, those rules had only allowed for third doses in some immunocompromised groups. Federal officials have warned providers against violating the agreements, which could jeopardize their access to the shots, liability protections, and reimbursements. 

However, as data emerged both of waning vaccine effectiveness in the United States and from successful booster programs rolled out abroad, some jurisdictions have already moved forward with their own booster shot programs.

Maryland earlier this month began offering booster shots to seniors in the state's nursing homes, allowing residents to "self-attest" whether they were sufficiently immunocompromised to be eligible for the doses. San Francisco made headlines last month for offering recipients of Johnson & Johnson's vaccine a "supplemental" dose of Moderna or Pfizer. 

More than two million Americans have so far already received an additional dose. Data from tracking side effects among those with an additional dose had so far not raised any safety concerns, CDC officials told the ACIP on Wednesday. 

The ACIP's recommendations, like the FDA's authorization, offer few answers for recipients of COVID-19 vaccines not made by Pfizer and its German partner BioNTech. 

Regulators are still reviewing a submission by Moderna, which sought permission last week for booster shots of its vaccine at 50 micrograms — half the dose of its first two shots. Johnson & Johnson has yet to announce an application for approval of a second dose for its vaccine, though federal health officials say they expect the submission soon. 

The ACIP and FDA also stopped short of allowing use of Pfizer's vaccine to boost recipients of Moderna or Johnson & Johnson's vaccine. Research backed by the National Institutes of Health examining the safety and efficacy of so-called "mix-and-match" boosting has yet to release results. 

Ahead of their vote Thursday, federal health officials and members of the ACIP acknowledged worries over recommending boosters for only one of the currently authorized vaccines. Beyond concerns of equity, some of the advisers warned the partial recommendation could pose logistical challenges to nursing homes and other congregate settings where not all of the residents would be eligible. 

"As a physician, I am frustrated, as I know many of you are, with the lack of data that would allow for a regulatory allowance," the FDA's Doran Fink told the committee. 

"FDA is is working diligently with vaccine manufacturers as well as with our other partners in federal government, including NIH, to arrive at a solution expediently to address the situation, and to provide a solution that will comply with legal requirements," added Fink later.