The FDA’s Vaccines and Related Biological Products Advisory Committee (VRMPAC) will meet on Thursday (26 January) to assess future vaccine regimens for COVID-19: considering questions around the composition and immunization schedules of authorized and approved COVID-19 vaccines and the question of annual administration.
Pharma giants such as Pfizer and Moderna have based their future forecasts on the concept of annual COVID-19 shots, although up to now there has been no official guidance or indications from regulators as to what long-term policy recommendations are likely to look like.
Now, in a briefing document for Thursday's meeting, the FDA says that "experience from influenza vaccine strain composition changes for U.S. vaccines suggests that implementation of an annual vaccine composition evaluation and recommendation would likely be practical for COVID-19 vaccines. Additionally, based upon modelling using the available evidence, in the absence of the emergence of a variant that essentially escapes protection conveyed by the existing vaccines, the administration of an updated vaccine on an annual basis also appears to be reasonable."
Annual shots
The FDA briefing document highlights the agency wants to find a ‘data-driven approach that is well founded, and similar in many ways to the process used for updating the composition of influenza vaccines.’
That could see the same COVID-19 vaccine compositions for primary series and booster vaccination; and the same composition of S protein sequence(s) contained or encoded in all COVID-19 vaccines in use in the US.
Unlike flu, no global health recommendations yet exist for annual COVID-19 immunizations: but the FDA wants to draw on evidence from the country so far to compile its strategy.
“The FDA expects that simplification of COVID-19 vaccine composition and annual immunization schedules may contribute to more facile vaccine deployment, fewer vaccine administration errors, and less complex communication, all potentially leading to improved vaccine coverage rates and, ultimately, to enhanced public health,” says the briefing document.
Mimicking flu shot schedules
Evidence on prior exposure and vaccinations suggests that most individuals will only need to receive one shot to restore protective immunity for a period of time, says the FDA.
Two doses may still be need in those with a low likelihood of prior exposure (the very young) or those who may not generate a protective immune response (older and immunocompromised individuals).
The current influenza vaccine antigen selection process may serve as a general framework for evaluating the selection of updated SARS-CoV-2 Spike protein sequences contained in COVID-19 vaccines.
“FDA anticipates conducting an assessment of SARS-CoV-2 strains at least annually and to engage VRBPAC in about early June of each year regarding strain selection for the fall season,” says the document.
“Subsequently, a decision on the recommended vaccine composition would be made in time for any updated vaccine to be in production in time to be deployed for use no later than September of each calendar year. Of note, circulation of a more pathogenic vaccine-escape variant of SARS-CoV-2 would likely prompt, on an as needed and emergent basis, an ad-hoc strain selection meeting of VRBPAC.”
Once an update of the COVID-19 vaccine composition for an upcoming vaccine campaign has been recommended by VRBPAC, FDA anticipates reviewing a comprehensive data package that may include manufacturing, non-clinical, and clinical data.
“With additional experience in current and improved methods for evaluating the effectiveness of COVID-19 vaccines and with additional experience in manufacturing, future updates to the COVID-19 vaccine composition may potentially be implemented without pre-authorization or pre-approval clinical data for vaccines for which efficacy has previously been demonstrated, similar to the annual strain selection process for seasonal influenza vaccines,” says the briefing document.