The Omicron variant has been reported in 57 nations, with COVID cases rising in southern Africa including Zimbabwe, and the number of patients needing hospitalization is likely to rise as it spreads, the World Health Organization said on Wednesday. The WHO, in its weekly epidemiological report, said more data was needed to assess the severity of disease caused by the Omicron variant and whether its mutations may reduce protection from vaccine-derived immunity. "Even if the severity is equal or potentially even lower than for Delta variant, it is expected that hospitalizations will increase if more people become infected and that there will be a time lag between an increase in the incidence of cases and an increase in the incidence of deaths," it said. Omicron can partially evade protection from two doses of vaccine made by Pfizer Inc and partner BioNTech, Alex Sigal, the research head of a South African laboratory, said on Tuesday. However, the study, based on preliminary data that has not yet been peer-reviewed, showed recipients of two vaccine doses who had a prior infection were mostly able to neutralize the variant, suggesting booster doses could help fend off infection.