WHO recommends that new COVID vaccines should target only XBB variants

As of May 2023, XBB.1 descendent lineages (XBB.1.5, XBB.1.16, XBB.1.9) are the predominant SARS-CoV-2 viruses circulating globally. As a result, the World Health Organization is recommending that new formulations of COVID-19 vaccines should aim to induce antibody responses that neutralize XBB descendent lineages, in order to improve protection, particularly against symptomatic disease. For example, vaccine manufacturers could use a monovalent XBB.1 descendent lineage, such as XBB.1.5 or XBB.1.16 as the vaccine antigen. However, other formulations and/or platforms that achieve robust neutralizing antibody responses against XBB descendent lineages could also be considered.1,2 The WHO stresses that currently approved COVID-19 vaccines, including those based on the original (index) virus, continue to provide protection against severe disease and death, which is the primary objective for COVID-19 vaccination. However, protection against symptomatic disease is limited and less durable. New COVID-19 vaccine formulations are needed to improve protection against symptomatic disease.1 The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) advises moving away from including the original virus strain in future formulations of COVID-19 vaccines for several reasons: the index virus and antigenically closely related variants are no longer circulating in humans the index virus antigen elicits undetectable or very low levels of neutralizing antibodies against currently circulating SARS-CoV-2 variants, including XBB descendent lineages inclusion of the index virus in bi- or multivalent vaccines reduces the concentration of the new target antigen(s) as compared to monovalent vaccines, which may decrease the magnitude of the humoral immune response immune imprinting due to repeated exposure to the index virus may reduce immune responses to new target antigen(s).1,2 The WHO recommendation for vaccine composition change is intended to inform future formulations of COVID-19 vaccines made by all vaccine manufacturers.1 Pfizer/BioNTech, Moderna and Novavax are already developing versions of their respective vaccines targeting XBB.1.5 and other currently circulating strains.3 The WHO emphasizes that until vaccines with updated (XBB) antigen composition are authorized and available, the best protection against COVID-19 will be achieved by continued use of currently approved vaccines, in combination with public health and social measures to prevent infection.2 References 1. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. May 18, 2023. (accessed May 30, 2023). 2. World Health Organization. Annex: Statement on the antigen composition of COVID-19 vaccines. May 18, 2023. (accessed May 30, 2023). 3. WHO recommends new COVID shots should target only XBB variants. Medscape Pharmacists, May 19, 2023. (accessed May 30, 2023).

WHO recommends that new COVID vaccines should target only XBB variants

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