Credit CDC Nowcast
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As the CDC Nowcast graphic above illustrates, XBB COVID variants have supplanted all of the major variants that were in play last summer (largely BA.4 & BA.5) when the United States developed their last updated (bivalent) COVID booster shots that were released last fall.
Those shots - while still useful in reducing the severity of COVID infections - now provide only limited (and relatively short-lived) protection against infection with these newer variants.
Thirty days ago the WHO Advisory Committee (TAG-CO-VAC) recommended that countries switch to a monovalent COVID Vaccine next fall based on either XBB.1.5 or XBB.1.6. Two weeks ago the ECDC/EMA issued a similar report (see ECDC-EMA Statement on Updating COVID-19 Vaccines Composition).
Last April the FDA signaled they would be releasing their own recommendations in early summer. On Friday (June 16th), the FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) released the following recommendation:
FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) met on June 15, 2023, to discuss and make recommendations for SARS-CoV-2 strain(s) for updated COVID-19 vaccines for use in the United States beginning in the fall of 2023.
For the 2023-2024 formulation of the COVID-19 vaccines for use in the U.S. beginning in the fall of 2023, the committee unanimously voted that the vaccine composition be updated to a monovalent COVID-19 vaccine with an XBB-lineage of the Omicron variant. Following discussion of the evidence, the committee expressed a preference for XBB.1.5.
During this meeting, the advisory committee was informed of the manufacturing timelines, they reviewed the available data on the circulation of SARS-CoV-2 virus variants, current vaccine effectiveness, human immunogenicity data of current vaccines against recently circulating virus variants, the antigenic characterization of circulating virus variants, animal immunogenicity data generated by new candidate vaccines expressing or containing updated spike components, and preliminary human immunogenicity data generated by one XBB.1.5 candidate vaccine.
Based on the totality of the evidence, FDA has advised manufacturers who will be updating their COVID-19 vaccines, that they should develop vaccines with a monovalent XBB 1.5 composition.
The June 15 VRBPAC is in follow-up to the January 26, 2023, VRBPAC at which FDA discussed the process for determining the need for recommending updates to the composition of COVID-19 vaccines, and the timing for implementation of such an update.
FDA will continue to monitor the safety and effectiveness of the COVID-19 vaccines and the evolution of the SARS-CoV-2 virus.
Additional information: Recommendation for the 2023-2024 Formula of COVID-19 vaccines in the U.S.
The gamble inherent in any vaccine strain selection is that there are no guarantees that the dominant SARS-CoV-2 variants of today will still be in control 4 or 6 months from now. But even if that happens, an updated XBB.1.5 vaccine is likely to be more effective than what we have now.
As with influenza, there is a pressing need for developing a `universal' vaccine; one that covers a wide range of variants rather than targeting just one or two.
This is a topic we looked at last March in Nature: CoV Recombination Potential & The Need For the Development of Pan-CoV Vaccines, where researchers warned of the potential future trajectory and impact of a SARS-MERS recombinant virus.
In sum, given the high risk of SARS-CoV-2/MERS-CoV recombination, the development of pan-β-CoV vaccines as well as CoV entry and replication inhibitor-based therapeutics is urgently needed to combat the pandemics or epidemics caused by emerging SARS-CoV-3 or MERS-CoV-2 in the future.
