Covid-19 research

Antibodies less effective against South African Covid strain, says French study

Scientists in France analysed the sensitivity of Sars-Cov-2 variants to neutralising antibodies generated by Pfizer BioNTech vaccine.
Scientists in France analysed the sensitivity of Sars-Cov-2 variants to neutralising antibodies generated by Pfizer BioNTech vaccine. THOMAS KIENZLE AFP/File

In a landmark study, scientists from France have determined the sensitivity of three different variants of Sars-Cov-2 to the neutralising antibodies generated in individuals who had previously contracted Covid-19 and in those who were vaccinated.

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Scientists from six prestigious French institutions* showed that both types of antibodies (naturally generated and vaccine induced) were able to neutralise the UK variant (B.1.1.7) to a same degree as the reference variant of the virus (D614G) that was until recently the most widespread in France.

However, the study showed that when it came to the South African variant (B.1.351), the neutralising effect was less effective.

According to Dr Thierry Prazuck, who is a co-author of the study, the analysis of the serum samples collected from 58 individuals up to nine months after the onset of symptoms showed that the antibodies neutralised the classic and the UK variant while 40 per cent of the samples lacked any activity against the South African strain.

“This does not necessarily mean that these patients will be infected with the South African strain. But it may increase the risk of infection as they have a limited immunity against it,” Dr Prazuck, Head of the Infectious Diseases Department at Orléans Regional Hospital, told RFI.

He added that to neutralise the South African variant, “the antibody concentrations needs to be around six times higher than for the classic variant.”

In the second part of the study, the scientists also analysed the serum samples of people who were administered the Pfizer BioNTech vaccine.

“We found that one or two weeks after the second dose of the vaccine, the level of neutralising antibodies was high enough in almost all the vaccinated volunteers, against the classic and the UK strain. But in this case too, the antibodies were less effective against the South African strain,” he said.

According to the study, while 80 percent of the serum samples were neutralising for the UK and the classic variants, only 60 percent of the samples were neutralizing for the B.1.351 variant.

Dr Prazuck also said that those who were infected with Covid-19 needed just one dose of the vaccine to get ample protection, while those who didn’t contract the disease needed two doses.

“Had there been no South African or Brazilian variants, with vaccination, you could say, people will be well protected from Covid-19 (including the UK strain). But we don’t know if the South African strain is going to spread further, and whether that would mean a risk of a second, perhaps mild, infection,” he added.

*Institut Pasteur, Orléans Regional Hospital, Tours University Hospital, Créteil Intercommunal Hospital, Strasbourg University Hospital, Georges Pompidou European Hospital.

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