South Africa's health minister has said that the government believes that vaccines and high levels of prior Covid-19 infections are helping to keep disease milder in a wave driven by the Omicron variant, reports Reuters.

There have been early anecdotal accounts suggesting that the Omicron variant driving the fourth wave, which saw the country report a record number of daily infections earlier this week, is causing less severe illness than previous variants in South Africa but scientists say it is too early to draw firm conclusions.

"We believe that it might not necessarily just be that Omicron is less virulent, but ... coverage of vaccination [and] ... natural immunity of people who have already had contact with the virus is also adding to the protection," Health Minister Joe Phaahla told a news conference. "That's why we are seeing mild illness."