JOHANNESBURG (Reuters) -South African President Cyril Ramaphosa, who tested positive for COVID-19 on Sunday, is still showing mild symptoms and has had to delay a booster vaccine he was due to receive this week, his office said on Monday.

       A statement from the presidency added that he reiterated a call for everyone to be vaccinated so as to reduce the chances of serious illness, hospitalization and death.

       Ramaphosa, who was given Johnson & Johnson's vaccine in February, tested positive the same day that he addressed a state memorial to the last leader of South Africa's white minority government, FW de Klerk, in Cape Town.

       His office said on Sunday that Ramaphosa had tested negative on Wednesday last week when he returned to South Africa from a trip to four West African countries.

       In the past few days South Africa has reported around 20,000 new COVID-19 infections a day, in a fourth wave believed to be linked to the Omicron coronavirus variant. South African scientists so far see no sign that the variant causes more severe illness.

       (Reporting by Alexander WinningEditing by Gareth Jones and Andrew Cawthorne)