The Omicron variant of SARS-CoV-2, the virus which causes COVID-19, was first identified in November this year in South Africa and Botswana.
The variant has been shown to be highly transmissible and have extensive evasion of neutralising antibody immunity elicited by vaccination and previous SARS-CoV-2 infection.
Infections from the variant are rapidly expanding worldwide.
The yet-to-be peer-reviewed study, posted on the pre-print repository MedRxiv, enrolled 15 previously vaccinated and unvaccinated people who were infected with the Omicron variant.
The scientists used plasma, a blood product which contains antibodies, from the participants to test the ability of the antibodies to control both Omicron and Delta in the lab — a so-called ‘neutralisation’ test.
They measured this close to when the participants had symptoms, and again around two weeks later.
The results show a developing antibody response to Omicron, with neutralisation increasing 14-fold over this time.
However, the team also observed that the participants developed some enhanced immunity against the Delta variant, with Delta neutralisation increasing 4.4-fold.
The researchers also show that vaccinated participants were able to mount a better neutralising response against Delta, while the response in unvaccinated participants was more variable.
”The increase in Delta variant neutralisation in individuals infected with Omicron may result in decreased ability of Delta to re-infect those individuals,” said Professor Alex Sigal, from Africa Health Research Institute.
”If Omicron does prove to be less pathogenic, then this may show that the course of the pandemic has shifted — Omicron will take over, at least for now, and we may have less disruption of our lives,” Sigal, who led the study, added.
The authors of the study noted that along with emerging data indicating that Omicron, at this time in the pandemic, is less pathogenic than Delta, such an outcome may have positive implications in terms of decreasing the COVID-19 burden of severe disease.