Africa's top public health agency is still talking to pharmaceutical firms Merck and Pfizer about obtaining supplies of their antiviral pills to treat Covid-19, its director said on Thursday.

"We are still in discussions with both Pfizer and Merck, so there's no new development that I can share. These discussions take long," said John Nkengasong, head of the Africa Centres for Disease Control and Prevention (CDC), at a regular online briefing.