Since they have been made available, COVID-19 vaccines have been updated several times regarding the groups eligible to receive them, the timing of primary series doses, the availability of and recommendations for post-primary-series doses and specific vaccine antigens (monovalent vs. bivalent antigens) that the vaccines contain. It is likely that further changes to COVID-19 vaccines will occur in the future. What might these changes look like and when might they happen?
What changes might be coming?
The most important change that is likely to come for COVID-19 vaccines in the near future is a move toward seasonal updates to COVID-19 vaccine antigens. The purpose of these changes would be to provide better immunological protection against circulating strains which do not match the antigenic composition of currently existing vaccines. This would mean that COVID-19 vaccines would be more like influenza vaccines, with updates made to the vaccine components each winter respiratory virus season.
These updates would likely be made after a meeting or several meetings with technical advisory groups, who would advise regulatory bodies about vaccine antigen components. The World Health Organization has a Technical Advisory Group on COVID-19 Vaccine Composition, which meets regularly to discuss SARS-CoV-2 evolution and to advise WHO on whether changes might be needed to the antigens of future COVID-19 vaccines globally. In May 2023, this group issued a statement suggesting that future vaccine components should contain an XBB.1-descendant lineage and that future vaccines should not contain “index virus” antigen (i.e., antigen based on the original form of SARS-CoV-2). Within the United States, FDA’s Vaccines and Related Biological Products Advisory Committee and the CDC’s Advisory Committee on Immunization Practices will likely be involved in the process of deciding on updates and recommending updated vaccines. FDA has already signaled that monovalent vaccines with the SARS-CoV-2 ancestral strain antigen only should no longer be used in the United States. Current vaccines available, and vaccines which will be administered in fall 2023, will be bivalent vaccines (containing the SARS-CoV-2 ancestral strain antigen + BA.4/BA.5 antigen).
It is not yet clear how frequently groups will plan to meet to discuss regular updates to COVID-19 vaccines. The frequency of meetings will depend both on the future patterns of SARS-CoV-2 seasonality as well as the pace at which SARS-CoV-2 mutations that are immunologically relevant occur. One potential option is that groups may meet at times similar to the technical advisory groups which discuss updates to influenza vaccines annually (in February for the Northern Hemisphere and in September for the Southern Hemisphere).
When might these changes happen?
It is likely that further updates to the vaccines will be considered carefully, taking into account circulating strains both within the U.S. and more broadly. If it is determined that an update would be needed, it is likely any update would be targeted for vaccines to be administered in fall/winter 2024. It is important to note that these changes are subject to several factors that are currently unknown, including further mutations to Omicron strains during the next winter respiratory virus season (2023-2024), as well as vaccine manufacturing capability.