Updating the Covid-19 vaccine: FDA offers a qualified thumbs-up ahead of adcomm
The FDA’s adcomm of outside vaccine experts will meet tomorrow to discuss how to protect the US from a likely coming wave of Omicron cases in the fall and winter, and whether to deploy vaccines that specifically target the Omicron variant.
While the data so far are limited, the FDA sounded an upbeat tone in the briefing documents on Pfizer/BioNTech’s candidates, released this weekend ahead of the VRBPAC meeting.
“The current epidemiology of SARS-CoV-2, the evidence of waning immunity elicited by current COVID-19 vaccines, and the available immunogenicity data generated from a limited number of variant-specific vaccine candidates suggest that an updated vaccine composition may provide added benefit against currently circulating virus variants,” the FDA said in its briefing documents, adding:
This may be particularly important as the 2022-2023 winter season progresses and the risk of another major COVID-19 outbreak increases due to the combination of waning immunity, further evolution of variants, and increased indoor activity. Nevertheless, as noted above, uncertainties remain, and there are potential trade-offs associated with various options for modifying the composition of current vaccines
However, the potential benefits of this updated vaccine will have to be weighed by the adcomm against multiple uncertainties, including unknown future variants, the dearth of clinical efficacy data for these boosters compared to the prototype vaccines, and potential manufacturing issues that might arise related to producing an updated vaccine formulation, FDA said.
Pfizer said on Friday that its Omicron-adapted monovalent candidate given as a fourth booster dose elicited a 13.5 and 19.6-fold increase in neutralizing geometric titers against Omicron BA. 1, while its bivalent vaccine candidate exhibited a 9.1 and 10.9-fold increase against Omicron.
“Based on these data, we believe we have two very strong Omicron-adapted candidates that elicit a substantially higher immune response against Omicron than we’ve seen to date. We look forward to discussing these data with the scientific community and health authorities so we may rapidly introduce an Omicron-adapted booster as soon as possible if authorized by regulators,” Pfizer CEO Albert Bourla said in a statement.
The agency offers the committee six options for making a strain recommendation:
- Make no recommendation and let the vaccine sponsors just work with FDA, although that may result in different compositions that are difficult to compare moving forward.
- Stick with the current composition of the vaccines – likely maintains good efficacy against severe disease, but the composition becomes increasingly distant from the circulating virus.
- Recommend that the composition of all boosters be updated to contain an Omicron component that has been tested clinically.
- Recommend that the composition of all vaccines used for booster doses be updated to contain a more recent Omicron component without clinical evidence.
- Recommend that the composition of all COVID vaccines used for both primary series and boosters be updated to contain an Omicron component, which might eliminate confusion but there’s no data on the efficacy of a primary series.
- Recommend that the composition of some vaccines used for booster doses be updated to contain something other than an Omicron component (e.g., Beta variant vaccine), which could provide additional choices but may be confusing for the public.
The voting question also seems to steer the panelists to not just weigh in on the Pfizer vaccine specifically, but to think about this situation holistically. The voting question is, “Does the committee recommend inclusion of a SARS-CoV-2 Omicron component for COVID-19 booster vaccines in the United States?”