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Public health agencies need to define the purpose of COVID boosters, or risk the public falling victim to "booster fatigue," the CDC's Advisory Committee on Immunization Practices (ACIP) said on Wednesday.

Agencies have been plagued by the lack of a clear voice in defining the exact purpose of the COVID vaccination strategy, and many ACIP members agreed that the time has come to clearly communicate to the public what existing authorized or approved COVID vaccines can and can't do.

"It feels inevitable, as if this is going to be ongoing," said Lynn Bahta, RN, of the Minnesota Department of Health in Saint Paul. "We need to be thinking about how to make a better vaccine."

Sarah Long, MD, of Drexel University in Philadelphia, was even more blunt, saying "we should not chase the rainbows" of preventing transmission, infection, or even mild disease.

While Long noted that current vaccines were less than effective against anything but preventing severe disease and death, she implicated the virus itself rather than the vaccines for this shortcoming.

"The likelihood is there is no infection due to coronavirus that will protect against subsequent infection," she said.

Beth Bell, MD, of the University of Washington in Seattle, expressed concern about "booster fatigue" and said that multiple boosters give "the impression that the vaccines aren't effective."

"People are losing confidence in the vaccination program," she said.

While data presented by CDC staff showed modest benefits of boosters, they also did not reveal any additional harms. Incidence of vaccine-associated myocarditis and pericarditis were lower than after the primary series, and there was no evidence of "immune tolerance," where additional COVID vaccines led to lower antibody levels or T-cell exhaustion. Sara Oliver, MD, of the CDC, noted that Israeli data found antibody levels after a fourth dose returned to levels seen after a third dose.

There was also no evidence of "imprinting," or that exposure to one strain "primes B-cell memory and limits the development of memory B cells and neutralizing antibodies against new strains," Oliver added. She pointed to data that showed a "diverse response" to a number of variants following a booster dose, whether it was targeting the ancestral strain or other variants.

Wilbur Chen, MD, of the University of Maryland in Baltimore, was reassured by this data, saying given the lack of evidence for imprinting, he felt "encouraged that future boosting would be appropriate."

He also encouraged trying to tailor future vaccine strategies for different populations, such as antibody tests for immunocompromised individuals before a booster is required.

Oliver Brooks, MD, of Watts HealthCare Corporation in Los Angeles, also agreed that while simpler communication about vaccination strategies might be the goal, it also might not be possible, and urged the committee, "don't be afraid of complexity."

"There may be almost no way that it's going to be a simple recommendation," he said, emphasizing the need to "keep the public engaged and fully confident and comfortable" with vaccine recommendations going forward.

"Don't overpromise with the vaccines," Brooks added.

ACIP chair, Grace Lee, MD, of Stanford University in California, acknowledged the challenge of trying to "pursue a precision public health strategy" on a population level.

"At some point, we've had different objectives, [but] we need a shared vision and a goal for what we're trying to achieve," she noted, adding that public health agencies need to "communicate using a common language."

"We need to think carefully about the data tools we would need to help us be responsive," said Lee, adding that it would "help to understand the uncertainty in front of us today."

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