The Omicron variant of the coronavirus can partially evade the protection from two doses of Pfizer Inc and partner BioNTech's Covid-19 vaccine, according to the research head of a laboratory at the Africa Health Research Institute in South Africa.

Still, the study showed that blood from people who had received two doses of the vaccine and had a prior infection were mostly able to neutralise the variant, suggesting that booster doses of the vaccine could help to fend off infection.

Alex Sigal, a professor at the Africa Health Research Institute, said on Twitter there was "a very large drop" in the neutralisation of the Omicron variant relative to an earlier strain of Covid-19.

Read the full Reuters story here.