Vaccine adcomm recommends harmonizing COVID-19 shots

Regulatory NewsRegulatory News | 26 January 2023 |  By 

A panel of vaccine and infectious disease experts recommends that the US Food and Drug Administration (FDA) harmonize COVID-19 vaccine composition and base future shots on the most prevalent circulating strain or strains of the SARS-CoV-2 virus.
At a 26 January virtual meeting of the FDA Vaccines and Related Biological Products Advisory Committee, FDA officials said that the agency supports the use of the same vaccine strain composition for primary series and booster doses, simplifying COVID-19 immunization schedules, as well as routine periodic strain selection procedures.
After a long day of debating vaccine clinical trial data and hearing from experts on the current state of the COVID-19 pandemic, the VRBPAC members voted unanimously that the FDA should require vaccine manufacturers to harmonize the COVID-19 vaccine strain composition of primary series and booster doses in the US.
“It's simply a fact that the authorized and approved COVID-19 vaccines would help to significantly reduce the morbidity and mortality from SARS-CoV-2,” said Peter Marks, director of the FDA Center for Biologics Evaluation and Research (CBER). “That said, these vaccines were developed in record time during a period when we were and which we continue to be learning more from SARS-CoV-2, not just about the virus but how it causes disease and especially how rapidly it can evolve.”
Marks and other FDA officials noted that since the initial strain of SARS-CoV-2 swept the globe, there have been dozens of new variants overtaking one another over the past three years. That rapid evolution of the virus required FDA to adjust its public health approach; however, now in a “reasonable place” to step back and reflect on future developments of COVID-19 vaccines to see if the agency can simplify the vaccination review process, according to Marks.
David Kaslow, director of the FDA Office of Vaccines Research and Review (OVRR), noted that more than a dozen COVID-19 vaccines are on the FDA's radar. Further, several different immunization schedules are authorized and approved in the US, leading to complexities in implementation, use and communication. Ideally, he said, the same vaccine composition would be used for the primary series and booster doses in the future, and the agency can recommend a more simplified immunization schedule, potentially risk-based adjustments for factors such as age and comorbidities.
"This is a consequential meeting to determine if we've reached a point in the pandemic that allows for simplifying the use of current COVID-19 vaccines and if it is the moment to implement a more routine approach to periodically updating strain composition of these vaccines," said Kaslow.
Panelist Cody Meissner, professor of pediatrics at Geisel School of Medicine at Dartmouth University, noted that it is difficult to ascertain how often booster shots need to be administered. "I think we need to see what happens with the disease burden; we may or may not need annual vaccine shots,” he said. “It seems absolutely too early to me in this process to answer that question."
Meissner said that he’d like to continue to see data from the CDC on rates of disease and other relevant information to determine how often the COVID-19 vaccine needs to be updated.
Mark Sawyer, professor of clinical pediatrics at the University of California-San Diego, said that he agreed with the FDA's recommendation to harmonize vaccine composition but was concerned about having enough data to support vaccinating children under two.
Paul Offit, a professor of pediatrics at the Children’s Hospital of Philadelphia, said that it's important to keep up with the latest strain of the SARS-CoV-2 virus to try get ahead of the disease.
"The goal is to keep people out of the hospital," he said. "Some people are so medically frail that a mild infection could land them in the hospital. So, I think it's important to get closer to the strains that are circulating."
Offit noted that, unlike yearly influenza vaccines, the original SARS-CoV-2 vaccine still confers some immunity to patients so if people do not have the latest booster shot it’s not as big of a deal as not having the right influenza strain vaccine.
Pamela McInnes, former deputy director of the National Center for Advancing Translational Sciences at the National Institutes of Health, said that while she supports developing vaccines that look closest to the most prevalent strain out there, she argued that the data currently are not clear that bivalent boosters are significantly better than monovalent boosters.
"I don't think we have randomized comparisons to demonstrate protection against severe disease and I think it's a really problematic message for the community,” she said.
Bruce Gellin, chief of global public health strategy at the Rockefeller Foundation, said that despite the efficacy of the current vaccines, better ones are needed. He agreed that the FDA's new approach is a better one.
"We have to keep reminding ourselves this is not influenza and we need to keep paying attention to that to make sure we don't keep following that dogma because we're used to doing it," he said. "We'll try this out. I don't think we're setting this in stone and we'll see how it goes. We may need to adjust along the way."
In briefing documents for the meeting, the FDA said it anticipates conducting an assessment of SARS-CoV-2 strains at least annually and engaging VRBPAC around early June each year regarding strain selection for the fall. The short time frame seems to favor messenger RNA (mRNA) vaccine producers since their technology allows for a quick assessment and mass production. The agency said a decision on the recommended vaccine composition would be made in time for any updated vaccine to be deployed no later than September of each calendar year. It also noted that circulation of a more pathogenic variant of SARS-CoV-2 would likely prompt an ad-hoc strain selection meeting of VRBPAC.
During the meeting, vaccine developers said they also supported the FDA's proposed globally harmonized process to update COVID-19 vaccine composition similar to the flu vaccine.
"The time is now to define the strain selection process, the regulatory requirements and pathway for licensure of future variant vaccine updates of boosters and primary series vaccination," said Kena Swanson, vice president for vaccine research at Pfizer. "This will help maintain optimal protection against COVID-19 and enable a rapid public health response to emerging variants."
McInnes expressed frustration with a perception that the VRBPAC meeting was focusing on mRNA vaccines. She said mRNA vaccines were "phenomenal" in dealing with the initial problem of quickly developing a vaccine for SARS-CoV-2, but expressed concern that the bivalent and monovalent vaccines haven't been any compared in randomized trials to demonstrate superiority.
"I don't want this meeting to be hijacked by mRNA vaccines," said McInnes.
Acting VRBPAC Chair, Stanley Perlman, professor of pediatrics at the University of Iowa, noted that other non-mRNA vaccine developers were also at the meeting to speak about their vaccines.

VRBPAC Meeting Materials


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