A risk-based booster dose strategy for COVID-19 vaccines could target populations at risk of severe disease and those critical to the public health infrastructure, CDC staff said at a meeting of CDC’s Advisory Committee on Immunization Practices (ACIP) on Monday.
Though FDA has yet to review data on booster doses for COVID-19 vaccines among the general population, CDC staff presented a preliminary framework to determine those who might need it most, including older adults, long-term care facility residents, and healthcare workers.
CDC staff presented limited data that showed that vaccines remain effective at preventing hospitalization and severe disease, but could be less effective at preventing infection or milder symptomatic illness.
That would be fine for most populations, except as Sara Oliver, MD, of the CDC, pointed out, healthcare professionals who develop even mild illness are forced to call out sick for COVID-19, which strains the healthcare infrastructure. While limited data on vaccine effectiveness among frontline workers — including healthcare professionals — showed declines against the Delta variant, differences were not significant compared with a pre-Delta period.
However, recent data showed lower vaccine effectiveness against infection among long-term care facility residents since the Delta variant gained prominence in the U.S. Preliminary vaccine effectiveness estimates found that among adults ages 65 and older, vaccine effectiveness decreased against hospitalization, but remained high.
ACIP members disagreed about the need for booster doses, with some arguing that ensuring the unvaccinated receive the primary vaccination series should be the highest priority.
“We’ve got lots of vaccine. At the moment we don’t have a lot of evidence of reduced vaccine effectiveness … based on the current data,” said ACIP committee member, Beth Bell, MD, of the University of Washington in Seattle.
ACIP chair, Grace Lee, MD, of Stanford University in California, argued that it didn’t necessarily have to be an “either/or situation.”
“Where we are in the pandemic, it makes sense to prevent severe disease, hospitalization, and death,” and that would be achieved both by vaccinating those who were unvaccinated, as well as booster doses in populations vulnerable to severe illness and death.
Currently, third doses of vaccine are only authorized for certain immunocompromised populations, and CDC staff warned clinicians that any off-label use of vaccine for booster doses meant they would not be covered under the PREP Act, which provides immunity from liability to COVID-19 vaccinators.
ACIP member, Helen Keipp Talbot, MD, of Vanderbilt University in Nashville, said that the Biden administration had confused the issue by saying they would make boosters available by September 20, which many providers took as a tacit approval of booster doses, despite no authorization from the FDA.
She added that because they believed the White House had given its blessing, “many, many, many hospitals” started giving a third dose both to providers and patients, and stressed the need for these recommendations to come through “normal” regulatory avenues.
Pfizer Vaccine Approval Hailed as ‘Miraculous Accomplishment’
In what was merely a formality, the ACIP voted unanimously to recommend the Pfizer/BioNTech COVID-19 vaccine for individuals ages 16 and older under the terms of an FDA biologics license application (BLA). The 14-0 vote replaces the interim recommendation for the vaccine made when it was still under emergency use authorization (EUA) for this age group.
Several members took the time after the vote to reiterate how impressed they were by the work done by the FDA and CDC over the past 18 months, and the fact that there is now an approved COVID-19 vaccine was a testament to that hard work.
Kathleen Dooling, MD, of the CDC, emphasized the mountain of available evidence supporting the vaccine’s safety and efficacy. Whereas the EUA only had one phase II/III clinical trial with a median of 2 months of follow-up data, the BLA featured at least 6 months of data from these trials, plus “a plethora of observational studies” and “extremely high-quality, real-world evidence” from around the world.
“I can’t think of a vaccine where we’ve had more efficacy and effectiveness and adverse event data,” said ACIP committee member, Sarah Long, MD, of Drexel University in Philadelphia. “This vaccine is worthy of recommendation for what it does today and worthy of the trust of the American people.”
While there is an association between the vaccine and myocarditis in younger men, CDC staff put it into perspective with a benefits/risk chart projected out to a year, showing for every million doses of vaccine, there would be an estimated 73 myocarditis cases in boys ages 16-17 compared to 1,540 COVID-19 hospitalizations prevented.
Amanda Cohn, MD, of the CDC, also put in that outcomes of “this apparent vaccine-associated myocarditis are substantially better than myocarditis caused by other types of infections or vaccines.” CDC staff still said they will continue to evaluate the data for long-term outcomes.
ACIP members also emphasized the need to get the message out that the vaccine is safe and effective, and the need for other strategies to encourage vaccine uptake in underserved populations, such as employers giving time off for employees to get vaccinated.