There is no evidence at present that healthy children and adolescents need booster doses of COVID-19 vaccine, the World Health Organization's chief scientist Soumya Swaminathan said on Tuesday.

Speaking at a news briefing, she said that while there seems to be some waning of vaccine immunity over time against the rapidly spreading omicron variant of the coronavirus, more research needs to be done to ascertain who needs booster doses.

"There is no evidence right now that healthy children or adolescents need boosters. No evidence at all," she said.

Israel has begun offering boosters to children as young as 12, and the U.S. States Food and Drug Administration earlier this month authorized the use of a third dose of the Pfizer and BioNTech COVID-19 vaccine for children aged 12 to 15.

Last week Germany became the latest country to recommend that all children between ages of 12 and 17 receive a COVID-19 booster shot. Hungary has also done so.

Swaminathan said the WHO's top group of experts would meet later this week to consider the specific question of how countries should consider giving boosters to their populations.

"The aim is to protect the most vulnerable, to protect those at highest risk of severe disease and dying. Those are our elderly populations, immuno-compromised people with underlying conditions, but also healthcare workers," she said.