A vial containing Moderna COVID-19 booster vaccine at a vaccination center.（GETTY）

A vaccine advisory group for the World Health Organization said Tuesday that, at this point, it does not recommend additional, let alone annual COVID-19 booster shots for people at low to medium risk of severe disease. It advised countries to focus on boosting those at high risk—including older people, pregnant people, and those with underlying medical conditions—every six to 12 months for the near- to mid-term.

The new advice contrasts with proposed plans by US Food and Drug Administration, which has suggested treating COVID-19 boosters like annual flu shots for the foreseeable future. That is, agency officials have floated the idea of offering updated formulations each fall, possibly to everyone, including the young and healthy.

In a viewpoint published last May in JAMA, the FDA's top vaccine regulator, Peter Marks, along with FDA Commissioner Robert Califf and Principal Deputy Commissioner Janet Woodcock, argued that annual COVID booster campaigns in the fall, ahead of winter waves of respiratory infections—such as flu, COVID-19, and RSV—would protect health care systems from becoming overwhelmed. And they specifically addressed the possibility of vaccinating those at low risk.

"The benefit of giving additional COVID-19 booster vaccines to otherwise healthy individuals 18 to 50 years of age who have already received primary vaccination and a first booster dose is not likely to have as marked an effect on hospitalization or death as in the other populations at higher risk," the FDA officials wrote. "However, booster vaccinations could be associated with a reduction in health care utilization (e.g., emergency department or urgent care center visits)."

In a press briefing Tuesday, WHO advisors called the benefit of boosting those at low or even medium risk "actually quite marginal" and suggested that countries could roll back offering primary COVID-19 vaccination series to low-risk healthy children and teens based on country-specific conditions and resources.

Context and limits

These updated recommendations "reflect that much of the population is either vaccinated or previously infected with COVID-19, or both," said Hanna Nohynek, chair of the WHO's advisory groups, called SAGE for the Strategic Advisory Group of Experts on Immunization. But the advisor's updated guidance "reemphasizes the importance of vaccinating those still at risk of severe disease, mostly older adults and those with underlying conditions, including with additional boosters," she added.

Specifically, the WHO's SAGE considered high-risk groups: older adults; younger adults with significant comorbidities, such as diabetes and heart disease; people 6 months and older with immunocompromising conditions, such as people living with HIV and transplant recipients; pregnant people; and frontline health workers.

For these high-risk groups, SAGE recommended an additional booster six to 12 months after their last, given the current epidemiological conditions. The advisors noted that the advice is "time-limited" for the current situation, not one for annual or biannual shots to be offered in perpetuity. The scenario and overall recommendations could change depending on new, more virulent variants or future declines in COVID-19 spread, for instance.

Already, the United Kingdom and Canada have offered spring COVID-19 boosters to high-risk groups, including older people and those who have immunocompromising conditions. So far, the FDA has not indicated that it will do the same.