Statement on the antigen composition of COVID-19 vaccines

Key points:

  • SARS-CoV-2 continues to circulate and evolve with important genetic and antigenic evolution of the spike protein.
  • Monovalent XBB.1.5 COVID-19 vaccines across different platforms elicit broadly cross-reactive neutralizing antibody responses against circulating SARS-CoV-2 variants.
  • Given the current SARS-CoV-2 evolution and the breadth in immune responses demonstrated by monovalent XBB.1.5 vaccines against circulating variants, the TAG-CO-VAC advises retaining the current COVID-19 vaccine antigen composition, i.e. a monovalent XBB.1.5 as the COVID-19 vaccine antigen.

The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) continues to meet regularly to assess the implications of SARS-CoV-2 evolution for COVID-19 vaccine antigen composition and advise WHO on whether changes are needed to the antigen composition of future COVID-19 vaccines. In May 2023, the TAG-CO-VAC recommended the use of a monovalent XBB.1 descendent lineage, such as XBB.1.5, as the vaccine antigen. Several manufacturers (using mRNA and protein-based and viral vector vaccine platforms) have updated COVID-19 vaccine antigen composition to monovalent XBB.1.5 formulations which have been approved for use by regulatory authorities.

The TAG-CO-VAC reconvened on 4-5 December 2023 to review the genetic and antigenic evolution of SARS-CoV-2, the performance of currently approved vaccines against circulating SARS-CoV-2 variants, and the implications for COVID-19 vaccine antigen composition. The twice-yearly evidence review by the TAG-CO-VAC is based on the need for continued monitoring of the evolution of SARS-CoV-2 and the kinetics of vaccine-derived immunity.

Evidence reviewed

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