The WHO Continues Endorsing Monovalent XBB.1.5 COVID-19 Vaccines

The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) today announced that given the current SARS-CoV-2 coronavirus 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 (monovalent XBB.1.5) as the COVID-19 vaccine antigen.

Although neutralizing antibody titres have been shown to be important correlates of protection from SARS-CoV-2 infection and estimates of vaccine effectiveness (VE), there are multiple components of immune protection elicited by infection and/or vaccination.

Estimates of VE against currently circulating SARS-CoV-2 variants, including XBB descendent lineages, are limited in terms of the number of studies, geographic diversity, vaccine platforms evaluated, populations assessed, duration of follow-up and comparative estimates for monovalent XBB.1.5 vaccines versus other formulations.

As of December 13, 2023, data on the immune responses following XBB descendent lineage infection or XBB.1.5 vaccination are largely restricted to neutralizing antibodies, and data on other aspects of the immune response, including cellular immunity, are limited in terms of the number of studies, vaccine platforms evaluated, populations assessed, duration of follow-up and comparative estimates for monovalent XBB.1.5 vaccines versus other formulations.

The World Health Organization says other vaccine formulations and/or platforms that achieve robust neutralizing antibody responses against currently circulating variants, including XBB- and BA.2.86 descendent lineages, can also be considered.

Following WHO SAGE policy, vaccination programs can continue to use any of the 12 WHO emergency-use listed or prequalified COVID-19 vaccines.

As previously stated, the TAG-CO-VAC continues to encourage the further development of vaccines that may improve protection against infection and reduce transmission of the SARS-CoV-2 virus.