The vaccines from Oxford/AstraZeneca and Pfizer/BioNTech may be more effective against the Brazilian variant of coronavirus than previously thought, a new study suggests.

Research from Oxford University, which has not yet been peer-reviewed, measured the level of antibodies that can neutralise – or stop infection from – variants that are circulating, including from South Africa and Brazil.

It found vaccines do not work as well against the variants as against an original strain of coronavirus, but the P1 Brazilian variant may be less resistant to vaccine-induced antibodies than first feared.

The South African variant remains the most worrying, the study suggests, and should be the focus for manufacturers making new vaccines.

Professor Gavin Screaton, lead scientist on the paper, said: “This study extends our understanding the role of changes in the spike protein in escape from the human immune response, measured as neutralising antibody levels.

“The results suggest that P1 might be less resistant to vaccine and convalescent (Covid infection) immune responses than B1351 (South Africa), and similar to B117 (Kent).”

The study used blood samples from people who have natural antibodies generated from a Covid-19 infection and from those whose antibodies were induced by the Oxford or Pfizer vaccines.

It found a nearly three-fold reduction in the level of virus neutralisation by the antibodies generated by the Oxford and Pfizer vaccines for the Kent and Brazil variants when compared to an original strain.

The vaccines struggled more with the South African variant, with between a seven and nine-fold reduction in the level of virus neutralisation involving this variant.

Professor Andrew Pollard, chief investigator on the Oxford University vaccine trial, said: “These further efforts to investigate the relationship between changes in the virus and human immunity provide new insights that help us be prepared to respond to further challenges to our health from the pandemic virus, if we need to do so.”

Cases of the Brazilian and South African variants have been found in the UK, with surge Covid testing employed to help prevent their spread.