WHO, through the Technical Advisory Group on the Composition of COVID-19 Vaccines (TAG-CO-VAC), plays a crucial role in constantly evaluating and adapting vaccination strategies against COVID-19. This adaptation is essential in the context of the continuous evolution of the SARS-CoV-2 virus and its variants.
In May 2023, TAG-CO-VAC recommended the use of a monovalent vaccine derived from the XBB.1 line, such as XBB.1.5, as an antigen for COVID-19 vaccines. This recommendation came in response to the dynamics of virus evolution and the effectiveness of different vaccine compositions.
Several manufacturers, using mRNA, protein, and viral vector-based vaccine platforms, have updated the antigen composition of the COVID-19 vaccine to monovalent XBB.1.5 formulations that have been approved for use by regulatory authorities.
On December 4-5, 2023, TAG-CO-VAC met to review the genetic and antigenic evolution of SARS-CoV-2, the performance of currently approved vaccines against circulating SARS-CoV-2 variants, and implications for vaccine antigen composition COVID-19. The biannual evidence review by TAG-CO-VAC is based on the need for continuous monitoring of the evolution of SARS-CoV-2 and the kinetics of vaccine-derived immunity.
The evolution of SARS-CoV-2, including the genetic and antigenic characteristics of past and current variants, and the impact of SARS-CoV-2 evolution on neutralization and cross-protection after vaccination and/or infection. Vaccine efficacy (VE) of currently approved vaccines during XBB lineage circulation periods.
Antigenic mapping analyzing the antigenic relationships of SARS-CoV-2 variants using naïve animal sera and human sera after vaccination and/or infection. Preliminary immunogenicity data on the performance of currently approved vaccines against circulating SARS-CoV-2 variants using animal and human sera. Cellular immune responses (T and B cells) after vaccination and/or infection.
