The World Health Organization (WHO) has updated its recommendations regarding COVID-19 vaccinations, suggesting it is no longer necessary for regular, medium-risk adults to have booster shots. However, high-risk groups should get a booster between six to 12 months after their last vaccine.

The U.N. agency focused on vaccinating those facing the most significant threat of severe disease and death from COVID-19, considering the high-level population immunity worldwide due to widespread infection and vaccination.

The health agency defined high-risk populations as older adults and younger people with other significant risk factors. For this group, the agency recommends an additional vaccine shot six or 12 months after the latest dose, based on age and immunocompromising conditions.

Meanwhile, it said healthy children and adolescents were "low priority" for COVID-19 vaccination and urged countries to consider factors like disease burden before recommending the vaccination of this group. It said the COVID-19 vaccines and boosters were safe for all ages, but the recommendations considered other factors like cost-effectiveness.

The WHO said in September last year that the end of the pandemic was "in sight." In a briefing on Tuesday, the agency said its latest advice reflected the current disease picture and global immunity levels but should not be seen as long-term guidance over whether annual boosters would be needed.

The recommendations come as countries take differing approaches. For example, some high-income countries like the United Kingdom and Canada offer those at high-risk COVID-19 boosters this spring, six months after their last dose.

"The revised roadmap re-emphasizes the importance of vaccinating those still at risk of severe disease," said Hanna Nohynek, chair of the WHO's Strategic Group of Experts on immunization, which made the recommendations.

The committee also called for urgent efforts to catch up. Routine vaccinations were missed during the pandemic and warned of a rise in vaccine-preventable diseases like measles.

For COVID-19, it said that vaccines beyond the initial two shots and a booster were no longer routinely recommended for those at "medium risk" as benefits were marginal.