Researchers at the Africa Health Research Institute (AHRI) found that immunity against delta improved four-fold following an exposure to the omicron strain, which is spreading rapidly in the UK.
Omicron displaced delta as the dominant variant in circulation in London earlier this month, and is believed to be significantly more transmissible. It has driven a surge in cases across the UK with a record 129,471 daily cases reported on Tuesday.
The AHRI study, which involved 33 vaccinated and unvaccinated people, found that exposure to omicron rose 14-fold after infection. Protection against delta rose 4.4-fold against delta.
“The increase in delta variant neutralisation in individuals infected with Omicron may result in decreased ability of delta to re-infect those individuals,” the scientists who conducted the study said.
Alex Sigal, the study’s co-author, said that “less pathogenic” as it appears, “then this will help push delta out”. This could mean “the disruption Covid-19 has caused in our lives may become less,” he added.
According to an earlier South African study, there is reduced risk of hospitalisation and severe disease in people infected with Omicron compared with the Delta variant.
However, scientists have cautioned the authors say some of that is likely due to high population immunity in South Africa.
The UK Health Security Agency (UKHSA) estimates that someone with omicron is between 31 per cent and 45 per cent less likely to attend A&E and 50 per cent to 70 per cent less likely to be admitted to hospital than an individual with the Delta variant.
These findings are broadly in line with studies published earlier this month by Imperial College London and the University of Edinburgh.
The omicron variant, first detected in southern Africa and Hong Kong in November, has since spread worldwide and threatened to overwhelm hospitals in some countries.