In a recent briefing document released by the United States Food and Drug Administration (US-FDA) ahead of an advisory committee meeting scheduled for January 26, 2023, the national agency suggested that people should get annual coronavirus disease 2019 (COVID-19 ) vaccines. In addition, they proposed a system for updating these vaccines, similar to how flu shots are updated.
To date, the understanding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunology is incomplete. As it evolves rapidly and evades vaccine-induced immunity, federal agencies are seeking ways to boost the waning immunity to COVID-19. More importantly, they want to ease people’s ‘pandemic fatigue’ by simplifying vaccination for both healthcare providers and the public. All this at the same time as protection against the ever-evolving SARS-CoV-2 is being expanded.
Thus, there is an urgent need to establish a framework to inform periodic updates of the COVID-19 vaccine composition and recommend ways to simplify the immunization schedule for future vaccination campaigns.
In 2022, the Vaccines and Related Biological Products Advisory Committee (VRBPAC) held two meetings to discuss this framework for updated COVID-19 vaccine and SARS-CoV-2 strain composition for vaccines to be administered in fall 2022. Following these meetings, FDA approved four monovalent COVID-19 vaccines in the United States.
These were two messenger ribonucleic acid (mRNA) COVID-19 vaccines, Spikevax and Comirnaty. In addition, there was Janssen, an adenovirus type 26 vector vaccine, and Novavax.
The upcoming VRBPAC meeting
At the VRBPAC meeting scheduled for January 26, 2023, members will vote on one issue: ways to simplify the composition of currently approved COVID-19 vaccines, their dosing regimens and immunization schedules.
This simplification of vaccine composition should reduce complexity, decrease vaccine administration errors due to the complexity of the number of different vial presentations, and potentially increase vaccine compliance by allowing clearer communication.”
However, this would remain a matter of open debate whether to administer a two-dose series to young children not exposed to SARS-CoV-2, older adults (≥50 years) and immunocompromised individuals with weakened immunity. The remaining individuals will receive a single dose of vaccine, including young children who have received two or more doses of vaccine and older children.
Other meeting goals are to harmonize the strain composition of all COVID-19 vaccines to most likely mRNA vaccines and transition to a single vaccine composition for primary series and booster vaccination. Switching to one vaccine formulation for primary and booster vaccination would further simplify current vaccine use. In all likelihood, it would be a bivalent vaccine using the spike (S) protein of the ancestral SARS-CoV-2 strain and the Omicron BA.4/BA.5 subvariants.
Members will also discuss the design of a process for determining the need for periodic updates of COVID-19 vaccines and the timing of implementing the same. In all likelihood, they will make recommendations for the selection of vaccine strains based on prevalent and expected SARS-CoV-2 variants in June of each year, so that the vaccine will be ready for distribution in September. If the need arises, the FDA may convene an ad hoc strain selection meeting between routine processes to handle a more pathogenic SARS-CoV-2 variant.
Another noteworthy point is that discussions of strain selection would take into account SARS-CoV-2 epidemiology, antigenic characterization of its new strains/mutants, and the results of its surveillance, serology, and vaccine efficacy studies.
There is growing evidence that hybrid immunity confers significant protection against COVID-19. Thus, a simplified immunization schedule to be proposed by the FDA on January 26 appears possible. There are also sufficient data on vaccine immunogenicity from several sources, including vaccine manufacturers, researchers, and observational studies.
It suggests that boosting with bivalent mRNA vaccines elicits enhanced neutralizing antibody responses to Omicron subvariants. They provide adequate protection against symptomatic and severe COVID-19 and related emergency room visits and hospitalization. However, according to FDA officials, this data is difficult to sift through due to several factors, e.g. different populations assessed, different assays used and limited sample size.
To summarize, several factors created confusion regarding COVID-19 vaccination uptake and administration in the United States. Communications from US federal agencies changed rapidly due to multiple COVID-19 vaccine formulations, different immunization schedules for different population subgroups, and varying vaccine formulations for primary vaccination series and booster doses.
To deal with this situation, a data-driven approach like the one previously used to update the composition of flu vaccines could help. Thus, the FDA is coming up with a proposal to evaluate SARS-CoV-2 strains at least once a year and engage VRBPAC in early June each year to select vaccine strains for the upcoming fall season. It will ensure timely implementation of updated COVID-19 vaccines no later than September each year.