The more infectious Omicron variant of Covid-19 appears to produce less severe disease than the globally dominant Delta strain, but should not be categorised as “mild”, World Health Organisation (WHO) officials said.

Janet Diaz, WHO lead on clinical management, said early studies showed there was a reduced risk of hospitalisation from the variant first identified in southern Africa and Hong Kong in November compared with Delta.

There appears also to be a reduced risk of severity in both younger and older people, she told a media briefing from WHO headquarters in Geneva.

She did not give further details about the studies or the ages of the cases analysed, but the impact on the elderly is one of the big unanswered questions about the new variant as most of the cases studied so far have been in younger people.