The World Health Organization (WHO) with the support of the Strategic Advisory Group of Experts (SAGE) on Immunization and its COVID-19 Vaccines Working Group, continues to review the emerging evidence on the increasing seroprevalence rates against SARS-CoV-2 globally and the characteristics and potential benefits of hybrid immunity.
This statement reflects the current understanding of hybrid immunity and highlights the gaps in evidence and potential implications for vaccination schedules and strategies.
Key messages:
Current evidence suggests that immune protection against severe outcomes due to infection and vaccination is more robust than that due to infection, or vaccination alone. This is based on infections with the ancestral SARS-CoV-2 or pre-Omicron VOCs.
The duration of protection from hybrid immunity has not been fully characterized yet, and it is unclear whether hybrid immunity will continue to provide strong protection against new variants.
Emerging evidence suggests that Omicron infection offers limited protection against re-infection with Omicron sub-lineages.
Irrespective of infection history, achieving high primary vaccine series coverage remains the foremost priority. Countries and implementing partners should emphasize the urgent need to fulfill this primary objective by calling for vaccination of all adults, focusing on healthcare workers, immunocompromised individuals, and older persons in line with the SAGE Prioritization Roadmap. Booster doses are associated with enhanced protection against Omicron; high-priority use groups should similarly be prioritized for these.
WHO SAGE continues to review the evidence as it becomes available.
The full text of the interim statement is available here: https://www.who.int/news/item/01-06-2022-interim-statement-on-hybrid-immunity-and-increasing-population-seroprevalence-rates
What is SAGE?
The Strategic Advisory Group of Experts (SAGE) on Immunization is the principal advisory group to WHO for vaccines and immunization. It is charged with advising WHO on overall global policies and strategies, ranging from vaccines and technology, research and development, to delivery of immunization and its linkages with other health interventions. SAGE is concerned not just with childhood vaccines and immunization, but all vaccine-preventable diseases. Further information: https://www.whoint/immunization/policy/sage/en
What is SAGE “interim statement”?
SAGE Interim Statements summarize the available body of evidence on a topic of contemporary debate, outlining the key considerations and research gaps to guide policymakers. Interim Statements summarize the current state of ongoing research and do not constitute a change in policy recommendations.
Updated WHO SAGE Roadmap for prioritizing uses of COVID-19 vaccines
he revised Roadmap (updated on 21 January 2022) takes into account increasing vaccine availability, vaccine coverage rates, and the evolving epidemiological situation including COVID-19 variants of concern. Scenarios in which vaccination coverage exceeds 50% of the population are considered, as are topics such as vaccine use in children and adolescents and prioritization of additional and booster doses in relation to vaccination coverage rates.
To assist countries in developing recommendations for optimized use of vaccines against COVID-19,priority-use groups for vaccination (both primary series and booster doses) are identified based on epidemiological scenarios, public health goals, and vaccine coverage scenarios. Further information: https://www.who.int/news/item/21-01-2022-updated-who-sage-roadmap-for-prioritizing-uses-of-covid-19-vaccines
What are WHO SAGE current booster recommendations?
WHO recommends a primary series and booster dose to be given to all individuals over the age of 18, starting with high priority-use groups. The booster is to be administered 4 to 6 months after the primary series. The number of doses required by each vaccine product varies. WHO does not currently recommend that children and young adults under the age of 18 receive a booster dose.
Currently WHO recommends an extended primary series (i.e. third dose) as well as a booster dose (i.e. fourth dose) for persons with moderate to severe immunocompromising conditions, for all COVID-19 vaccines. Homologous (same vaccine platform) and heterologous (different vaccine platform) vaccines can be used for such booster doses.
About WHO
The World Health Organization provides global leadership in public health within the United Nations system. Founded in 1948, WHO works with 194 Member States, across six regions and from more than 150 offices, to promote health, keep the world safe and serve the vulnerable. Our goal for 2019-2023 is to ensure that a billion more people have universal health coverage, to protect a billion more people from health emergencies, and provide a further billion people with better health and wellbeing.