The World Health Organization, 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 need for and timing of additional booster doses for the currently available COVID-19 vaccines which have received Emergency Use Listing (EUL).
WHO with support of SAGE has reviewed the available data from seven studies published so far, which show some short-term benefit of an additional booster dose in the highest risk group (health workers, those over the age of 60 and immunocompromised persons).
However, the data is only available for the mRNA vaccines and there is limited data regarding the duration of protection and the benefits of an additional booster dose for healthy younger people.
More data is needed to evaluate the benefits of an additional booster dose for other population groups and vaccine platforms.
When this is available, SAGE will update its recommendations accordingly.
Countries considering introducing a fourth additional booster dose should carefully weigh up the financial and programmatic challenges against the incremental benefits expected.
Additional booster doses beyond the first booster dose are currently being offered by some countries (i.e. fourth dose to older adults and a fifth dose for immunocompromised persons).
Data on the usefulness of these additional booster doses is sparse and especially limited on the duration of further protection. Data on additional booster doses as of May 2022 only exists for the mRNA vaccines, and not for other vaccine platforms.
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