Schools should only close as a last resort while research is under way into whether the new coronavirus variants affect children differently, the World Health Organisation said Wednesday.

The debate on shutting schools during the Covid-19 pandemic has been revived by the emergence of more contagious virus mutations.

The WHO said research had begun looking at the factors that may put children at risk, the long-term health effects on those infected, and the impact of new variants of SARS-CoV-2, the virus that causes Covid-19 disease.