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.
  • The objective of an update to COVID-19 vaccine antigen composition is to enhance vaccine-induced immune responses to circulating SARS-CoV-2 variants.
  • As the virus is expected to continue to evolve from JN.1, the TAG-CO-VAC advises the use of a monovalent JN.1 lineage as the antigen in future formulations of COVID-19 vaccines.
  • In accordance with WHO SAGE policy, vaccination programmes should continue to use any of the WHO emergency-use listed or prequalified COVID-19 vaccines and vaccination should not be delayed in anticipation of access to vaccines with an updated composition.

The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) meets regularly to assess the impact of SARS-CoV-2 evolution on the performance of approved COVID-19 vaccines. This includes meeting in person approximately every six months to determine the implications of SARS-CoV-2 evolution on COVID-19 vaccine antigen composition and to advise WHO on whether changes are needed to the antigen composition of future COVID-19 vaccines. 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 and protection of vaccine-derived immunity.

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. In December 2023, the TAG-CO-VAC advised retaining the use of a monovalent XBB.1 descendent lineage, such as XBB.1.5, as the vaccine antigen. Several manufacturers (using mRNA, protein-based and viral vector vaccine platforms) have developed COVID-19 vaccines with a monovalent XBB.1.5 formulation which have been approved for use by regulatory authorities and introduced into COVID-19 vaccination programmes in some countries. Previous statements from the TAG-CO-VAC can be found on the WHO website.

The TAG-CO-VAC reconvened on 15-16 April 2024 to review the genetic and antigenic evolution of SARS-CoV-2; immune responses to SARS-CoV-2 infection and/or COVID-19 vaccination; the performance of currently approved vaccines against circulating SARS-CoV-2 variants; and the implications for COVID-19 vaccine antigen composition.

Evidence reviewed

The published and unpublished evidence reviewed by the TAG-CO-VAC included: (1) SARS-CoV-2 genetic evolution with support from the WHO Technical Advisory Group on SARS-CoV-2 Virus Evolution

/Public Release. View in full here.