Pfizer Inc and BioNTech's Covid-19 vaccine appeared to only lose a small bit of effectiveness against an engineered virus with three key mutations from the new variant found in South Africa, according to a laboratory study conducted by the US drugmaker.

The study by Pfizer and scientists from the University of Texas Medical Branch (UTMB), which has not yet been peer-reviewed, showed a less than two-fold reduction in antibody titer levels, indicating the vaccine would likely still be effective in neutralising a virus with the so-called E484K and N501Y mutations found in the South African variant.

The study was conducted on blood taken from people who had been given the vaccine. Its findings are limited, because it does not look at the full set...