Countries should consider giving a second Covid-19 vaccine booster to the elderly, pregnant women, health workers, people with weaker immune systems and those at higher risk of severe disease, according to a team of experts from the World Health Organization (WHO).
Most Covid-19 vaccines consist of a primary series of two doses, with a first booster administered some four to six months after completion to improve immune response.
While several countries had rolled out the second booster dose against Covid, the WHO had so far not recommended it.
But after a meeting, last week, the Strategic Advisory Group of Experts (SAGE) on Immunization recommended the fourth dose or the second booster against Covid, but only for the vulnerable people.
“There is increasing evidence on the benefits of a second booster dose of vaccines in terms of restoring waning vaccine effectiveness (VE),” the SAGE said in a statement.
Protection offered by current vaccines declines substantially within a few months, particularly in the context of each variant of concern.
The guidance focuses on the need for a second booster as Omicron remains the dominant variant. It does not take into account future variants, or variant-containing vaccines, which are in late-stage development.
Factors such as waning vaccine- and infection-induced immunity, relaxation of public health measures, temporal fluctuations in transmission, and the potential emergence of new variants, may lead to Covid surges in the coming months, which could prompt the need for second booster doses.
“Evolving evidence from studies suggests that additional protection of the most vulnerable populations, at least for several months, is likely to be achieved through administration of a second booster dose, although follow-up time for these studies is limited,” the SAGE noted.
The second booster should be offered four to six months after the last dose, or as soon as possible thereafter.
WHO further recommends that countries also consider administering Covid-19 vaccines alongside the seasonal flu vaccine, where feasible.