The WHO Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) continues to closely monitor the genetic and antigenic evolution of SARS-CoV-2 variants, immune responses to SARS-CoV-2 infection and COVID-19 vaccination, and the performance of COVID-19 vaccines against circulating variants. Based on these evaluations, WHO advises vaccine manufacturers and regulatory authorities on the implications for future updates to COVID-19 vaccine antigen composition. The next decision-making meeting of the TAG-CO-VAC is scheduled for May 2025, after which a statement on COVID-19 vaccine antigen composition and an accompanying data annex will be published on the WHO website. These meetings are timed to balance the availability of the latest epidemiological, immunological, and virological data, with the kinetics of vaccine-induced protection and the lead time manufacturers need to update the antigen composition of authorized COVID-19 vaccines. The purpose of this statement is to guide the scientific community and vaccine manufacturers as to which data should be generated ahead of the May 2025 TAG-CO-VAC deliberations. It is an update to the previous statement on the types of data requested in October 2024.1 To inform decisions on COVID-19 vaccine antigen composition,2-6 the TAG-CO-VAC reviews data (see Table) on the genetic evolution of SARS-CoV-2 and the antigenic characteristics of previously and currently circulating variants. This includes the analysis of animal antisera following primary infection or vaccination in one-way and two-way neutralization tests, as well as immunogenicity data that assess the breadth and durability of immune responses, including neutralizing antibody responses, using sera from sequentially immunized or infected animals and pre-and post-vaccination human sera. The TAG-CO-VAC also considers vaccine effectiveness (VE) estimates of currently approved COVID-19 vaccines, particularly those that control for time since vaccination and that provide variant-specific estimates across different vaccine platforms for protection against any infection, symptomatic disease, and severe disease. Further examples of published data reviewed by TAG-CO-VAC and used to inform decisions on COVID-19 vaccine antigen composition can be found in the annexes accompanying each of the previous statements.2-6In addition, the TAG-CO-VAC reviews available data from vaccine manufacturers, including animal and human studies demonstrating the breadth and durability of immune responses elicited by currently authorized vaccines, as well as any vaccine candidates in development. For vaccine candidates in development, the TAG-CO-VAC highlights the utility of clinical immunogenicity data for decision-making on COVID-19 vaccine antigen composition. The TAG-CO-VAC also notes that comparable immunogenicity data (i.e. to the same variants) from previous vaccine compositions are especially useful. Vaccine manufacturers are also asked to provide observational epidemiological data that demonstrate the efficacy or effectiveness of their authorized COVID-19 vaccines, as well as any vaccine candidates in development. At this stage, the key antisera and antigens of interest for the May 2025 decision-making meeting for demonstrating breadth include antisera to: BA.2 (other historical reference viruses – e.g., index virus, Alpha, BA.1 – are also useful for determining antigenic relationships), XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging SARS-CoV-2 variants. Antisera of interest are animal sera after single or sequential exposure and human sera after a boost with monovalent JN.1, KP.2 or XBB.1.5 vaccines. Both pre- and post-vaccination sera should be included and, for all antisera, neutralizing antibody titers should be analyzed against at least one variant that emerged after the vaccine antigen, where feasible. Analysis of these antisera against the same panel of virus antigens as well as other new emerging SARS-CoV-2 variants will provide insight into antigenic characteristics of previous and emerging variants. Emerging variants include the list of SARS-CoV-2 Variants of Interest (VOI) and Variants Under Monitoring (VUM) maintained on the WHO website. Relative VE estimates should be calculated during periods of circulation of XBB, JN.1, KP.3.1.1, XEC or other emerging variant(s) in human populations across age groups, with separate VE estimates for each of the following vaccine antigen compositions: monovalent JN.1, monovalent KP.2 or monovalent XBB.1.5. Where available, the underlying rates of disease outcomes used to derive the relative VE estimates should also be provided.In preparation for the May 2025 meeting, the TAG-CO-VAC encourages the scientific community and vaccine manufacturers to prioritize generating and sharing the data outlined in the Table below to ensure evidence-informed deliberations on COVID-19 vaccine antigen composition; please contact the TAG-CO-VAC Secretariat: [tagcovac@who.int].
Type of data Comments SARS-CoV-2 genetic evolution Key variants include the list of Variants of Interest (VOI) and Variants Under Monitoring (VUM). This list is maintained on the WHO website.+ Antigenic characterization of previous and emerging SARS-CoV-2 variants Animal sera following primary infection or vaccination against each of the following variants: BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging variants* analyzed in one-way and two-way neutralization tests (pseudotype and live virus neutralization assays). Preliminary immunogenicity data on breadth and durability of immune responses following vaccination or infection with SARS-CoV-2 variant antigens. Neutralization of various representative viruses by non-naïve animal sera (e.g., sequentially immunized or infected), for each of the following antigens: BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and emerging variants;* Neutralization of various representative viruses (BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging variants*) by both pre- and post-vaccination human sera. Vaccinee sera should be analyzed in priority order: JN.1, KP.2, XBB.1.5;Neutralization of variants (BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging variants*) by sera from cohorts that are representative of recent population immunity. Vaccine effectiveness (VE) estimates of currently approved vaccines Relative VE estimates during periods of circulation of XBB, JN.1, KP.3.1.1, XEC or emerging variant(s) * in human populations. Studies need to estimate relative VE by time since vaccination or at least provide a measure of time since vaccination, such as the mean or median. They should also provide variant-specific estimates and distinct estimates for each of the following vaccine antigen compositions across different vaccine platforms: monovalent JN.1, monovalent KP.2, or monovalent XBB.1.5. Studies should also provide relative VE for a range of outcomes beyond severe disease, including any infection or symptomatic disease. Severe disease should not be defined using generic hospital admission data, but rather with specific criteria such as oxygen use, ventilation, or admission to intensive care due to respiratory symptoms. Where available, underlying rates of disease outcomes used to estimate the relative VE should also be provided. Data from vaccine manufacturers Animal and human data that demonstrate the breadth and durability in immune responses elicited by vaccines in current portfolio, as well as any vaccine candidates in development, against BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging variants;*Observational epidemiological data that demonstrate the efficacy or effectiveness of any vaccines in current portfolio, as well as any vaccine candidates in development, against BA.2, XBB.1.5, JN.1, KP.2, XEC, LP.8.1, LF.7.2 and potentially emerging variants.* + WHO website: https://www.who.int/activities/tracking-SARS-CoV-2-variants * Key emerging variants that evolve and considered relevant for demonstrating breadth include the list of Variants of Interest (VOI) and Variants Under Monitoring (VUM). This list is maintained on the WHO website: https://www.who.int/activities/tracking-SARS-CoV-2-variants ReferencesWorld Health Organization. Types of data requested to inform December 2024 COVID-19 vaccine antigen composition deliberations. 7 October 2024. Available from: https://www.who.int/news/item/07-10-2024-types-of-data-requested-to-inform-december-2024-covid-19-vaccine-antigen-composition-deliberationsWorld Health Organization. Interim statement on the composition of current COVID-19 vaccines. 17 June 2022. Available from: https://www.who.int/news/item/17-06-2022-interim-statement-on–the-composition-of-current-COVID-19-vaccines. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. 18 May 2023. Available from: https://www.who.int/news/item/18-05-2023-statement-on-the-antigen-composition-of-covid-19-vaccines. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. 13 December 2023. Available from: https://www.who.int/news/item/13-12-2023-statement-on-the-antigen-composition-of-covid-19-vaccines. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. 26 April 2024. Available from: https://www.who.int/news/item/26-04-2024-statement-on-the-antigen-composition-of-covid-19-vaccines. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. 23 December 2024. Available from: https://www.who.int/news/item/23-12-2024-statement-on-the-antigen-composition-of-covid-19-vaccines
Types of data requested to inform May 2025 COVID-19 vaccine antigen composition deliberations
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