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Current COVID-19 vaccines may need to be updated to ensure their continued effectiveness against omicron and future variants, an expert group appointed by the World Health Organization (WHO) has said.
The opinion is contained in an interim statement from the WHO Technical Advisory Group on COVID-19 Vaccine Composition, which was established in September 2021.
The Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) reviews and assesses the public health implications of emerging SARS-CoV-2 Variants of Concern (VOC) on the performance of COVID-19 vaccines and to provide recommendations to WHO on COVID-19 vaccine composition, as needed.
In the context of the circulation of Omicron SARS-CoV-2 Variant of Concern, the TAG-CO-VAC urges broader access globally to current COVID-19 vaccines for primary series and booster doses, in the hope that this also mitigates the emergence and impact of new VOCs.
The TAG-CO-VAC is considering the strain composition of COVID-19 vaccines and encourages vaccine developers to gather data on a small scale on the breadth and magnitude of immune response for monovalent and multivalent vaccines against VOCs.
The 18 experts are developing a framework to analyze the evidence on emerging VOCs “in the context of criteria that would trigger a recommendation to change COVID-19 vaccine strain composition and will advise WHO on updated vaccine compositions, as required.”
They said vaccines that have a high impact on the prevention of infection and transmission, in addition to the prevention of severe disease and death, are needed and should be developed.
“Until such vaccines are available, and as the SARS-CoV-2 virus evolves, the composition of current COVID-19 vaccines may need to be updated, to ensure that COVID-19 vaccines continue to provide WHO-recommended levels of protection against infection and disease by VOCs, including Omicron and future variants,” they said in the interim.
Since its emergence, the SARS-CoV-2 virus has continued to evolve, and WHO has designated five variants as SARS-CoV-2 Variants of Concern (VOC) to date – namely Alpha, Beta, Gamma, Delta, and Omicron – due to their impact on transmission, disease severity, or capacity for immune escape.
While the Omicron variant is spreading rapidly across the world, the evolution of SARS-CoV-2 is expected to continue and Omicron is unlikely to be the last VOC.
The TAG-CO-VAC is developing a framework to analyze the evidence on emerging VOCs in the context of criteria that would trigger a recommendation to change COVID-19 vaccine strain composition and will advise WHO on updated vaccine compositions, as required.
“This framework considers the global spread and transmissibility, clinical severity, genetic, antigenic and phenotypic characteristics of the VOC, including capacity for immune escape and assessments of vaccine effectiveness.”
The interim statement has it that with available COVID-19 vaccines, the current focus remains on reducing severe disease and death, as well as protecting health systems.
“Vaccines that have received WHO Emergency Use Listing, across several vaccine platforms, provide a high level of protection against severe disease and death caused by VOCs. For the Omicron variant, the mutational profile and preliminary data indicate that vaccine effectiveness will be reduced against symptomatic disease caused by the Omicron variant, but protection against severe disease is more likely to be preserved.
“However, more data on vaccine effectiveness, particularly against hospitalization, severe disease, and death are needed, including for each vaccine platform and for various vaccine dosing and product regimens,” they added.
In the interim, it has been highlighted that with near- and medium-term supply of the available vaccines, the need for equity in access to vaccines across countries to achieve global public health goals, programmatic considerations including vaccine demand, and evolution of the virus, a vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable.
The TAG-CO-VAC, it has been learnt, will consider a change in vaccine composition to ensure that vaccines continue to meet the criteria established in WHO’s Target Product Profile for COVID-19 vaccines, including protection against severe disease as well as to improve vaccine-induced protection.
“To that aim, COVID-19 vaccines need to be based on strains that are genetically and antigenically close to the circulating SARS-CoV-2 variant(s);
in addition to protection against severe disease and death, be more effective in protection against infection thus lowering community transmission and the need for stringent and broad-reaching public health and social measures;
elicit immune responses that are broad, strong, and long-lasting in order to reduce the need for successive booster doses.”
In the interim, the TAG-CO-VAC encourages COVID-19 vaccine manufacturers to generate and provide data on the performance of current and Omicron-specific COVID-19 vaccines, including the breadth, magnitude, and durability of humoral and cell-mediated immune responses to variants through monovalent and/or multivalent vaccines.
“These data will be considered in the context of the framework mentioned above to inform the TAG-CO-VAC decisions when changes to vaccine composition may be required.
“It would be important for vaccine manufacturers to take steps in the short-term for the development and testing of vaccines with predominant circulating variants and to share these data with the TAG-CO-VAC and other relevant WHO expert committees. Vaccine manufacturers are also encouraged to provide such data for any novel and broadly reactive SARS-CoV-2 vaccines that are developed.”
The TAG-CO-VAC will continue to assess evidence on the predominant circulating VOC(s) with respect to properties of spread/transmissibility, clinical severity (virulence), genetic, antigenic, and phenotypic characteristics of the VOC, including capacity for immune escape and assessments of vaccine effectiveness and impact, and information provided by manufacturers.
