Report on COVID-19 Vaccine Strains Promotes Updates on Vaccine Compositions

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The outcomes of a workshop organized by WHO and ICMRA regarding COVID-19 vaccine strain updates are presented in a report published by regulators.

The European Medicines Agency (EMA) announced on April 17, 2024 that a report was published by international regulators that details results from a workshop on COVID-19 vaccine strains. The workshop, organized by the World Health Organization (WHO) and the International Coalition of Medicines Regulatory Authorities (ICMRA), was held Feb. 26–27, 2024 to identify a process to optimize timely vaccine antigen composition recommendations and regulatory approvals. Participants in the workshop included representatives of national regulatory authorities, WHO, scientists, and industry.

The report, Global Perspectives on COVID-19 Vaccines Strain Update, highlights key regulatory considerations for updated COVID-19 vaccine composition and data requirements for the approval of strain changes (1). Virus evolution and circulation in different areas of the world are also discussed in the report. According to EMA, international regulators and WHO will create a structured process to support and optimize the timing of COVID-19 vaccine antigen recommendations.

Authorized COVID-19 vaccines are effective at preventing severe disease and hospitalization, according to EMA, but their protection weakens over time and against new strains of the virus. Therefore, updated vaccines must be developed and reviewed for approval, according to the agency. “Meeting participants stressed that international convergence on the process and timing of COVID-19 vaccine strain updates are therefore critical in view of the continuous evolution of SARS-CoV-2,” EMA stated in a press release.

According to the report, variants of SARS-CoV-2 continue to be derived from Omicron with the predominant variant being JN.1; however, WHO has concluded that JN.1 has “no increase in severity, reduction in vaccine effectiveness against severe disease, or increased burden on national public health systems compared to other Omicron sub-lineages” (2).


WHO’s Technical Advisory Group on COVID-19 Vaccine Composition (TAG-CO-VAC) will meet every six months to review evidence on vaccine antigen composition updates, according to the report. Regulators will also continue to issue recommendations in their respective jurisdictions.

“Looking at the global picture, a strain recommendation by regulatory authorities in November/December or April/May should allow all authorized vaccine technologies (mRNA [messenger RNA], protein/adjuvanted, inactivated) to meet the start of the autumn vaccination campaign in both hemispheres. Ideally recommendations should not be delayed beyond May in the Northern Hemisphere and December in the Southern Hemisphere, unless required by the epidemiological situation. ICMRA will meet as needed to reach a harmonized approach among its members,” the report states.

The two organizations, ICMRA and WHO, agreed that the following data will be required for COVID-19 vaccines composition recommendations and approvals:

  • assessments of SARS-CoV-2 evolution and the impact of that evolution on antigenicity and immune escape
  • epidemiological and virological surveillance to determine if antigenically distinct emerging variants will displace circulating variants in the future
  • human and animal immune responses with the approved antigen composition to determine cross-reactivity against variants
  • estimates of effectiveness of current approved vaccines against variants
  • evaluation of investigational vaccines and updated antigen composition.

“This requires sustained global genetic surveillance and timely data submission, strengthened antigenic assessment of variants, sustained in-vitro virological assessment of variants, strengthened assessments of immune responses following infection and vaccination, continued evaluation of the effectiveness of COVID-19 vaccines and further clinical studies, including randomized clinical trials comparing COVID-19 vaccines,” the report states.