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 April 2023, that the advisory group would convene at least twice in 2023: once in May 2023 and again, approximately 6 months later. At each meeting, recommendations to either maintain current vaccine composition or to consider updates will be issued. This frequency of evidence review by the TAG-CO-VAC is based on the kinetics of vaccine-derived immunity and the need for continued monitoring of the evolution of SARS-CoV-2, and will be adjusted if and as necessary. The TAG-CO-VAC met on 11-12 May 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 objective of an update to COVID-19 vaccine antigen composition is to enhance vaccine-induced immune responses to circulating SARS-CoV-2 variants. This statement and the recommendation for change is intended for all vaccine manufacturers and is intended to inform future formulations of COVID-19 vaccines.
The TAG-CO-VAC recognizes and reiterates that currently approved COVID-19 vaccines, including those based on the index virus, continue to provide substantial protection against severe disease and death, which is the primary objective for COVID-19 vaccination. Currently approved COVID-19 vaccines should continue to be used in accordance with the , published in April 2023. Notwithstanding the protection against severe disease, protection against symptomatic disease is limited and less durable. New formulations of COVID-19 vaccines are needed to improve protection against symptomatic disease.
Evidence reviewed
The published and unpublished evidence reviewed by the TAG-CO-VAC included: (1) SARS-CoV-2 evolution, including genetic and antigenic characteristics of earlier and current SARS-CoV-2 variants, including XBB.1 descendent lineages, and its impact on cross-neutralization and cross-protection following vaccination and/or infection; (2) Vaccine effectiveness (VE) of currently approved vaccines during periods of XBB.1 descendant lineage circulation; (3) Antigenic cartography analyzing antigenic relationships of SARS-CoV-2 variants using naïve animal sera and human sera following vaccination and/or infection; (4) Preliminary preclinical data on immune responses in animal models, following infection with XBB.1 descendent lineages; (5) Preliminary preclinical immunogenicity data on the performance of candidate vaccines with updated antigens (data not shown); and (6) B cell memory responses following vaccination and/or infection.
