An omicron infection may protect against the delta variant, helping to lower the severity of the pandemic, a new study suggests.
Research from the Africa Health Research Institute found that the blood plasma of people infected with omicron was able to control delta in lab experiments.
Researchers discovered that the antibody response to omicron rose fourteenfold two weeks after an infection, but were surprised to find that neutralising antibodies against delta also increased more than fourfold.
They also showed that vaccinated participants were able to mount a better neutralising response against delta, while the response in unvaccinated participants was more variable.
Lead researcher Alex Sigal, a professor at AHRI in South Africa, said that if omicron was less severe as it looked to be from the recent data, "this will help push delta out".
“The increased neutralising immunity against omicron was expected – that is the virus these individuals were infected with,” he said.
“However, we also saw that the same people – especially those who were vaccinated – developed enhanced immunity to the delta variant.
“If, as it currently looks like from the South African experience, omicron is less pathogenic, then this will help push delta out, as it should decrease the likelihood that someone infected with omicron will get re-infected with delta.”
The scientists said that if omicron could displace delta without while causing less severe disease it could have a major impact on the future of the pandemic.
"If so, then the incidence of Covid-19 severe disease would be reduced and the infection may shift to become less disruptive to individuals and society,” added Prof Sigal.
Previous studies in South Africa have shown that people who were infected with delta had better protection against omicron suggesting cross-protection.
Mounting evidence suggests that omicron is less severe than delta, with Edinburgh University finding that the risk of hospitilisation falls by a third with the newpeople two thirds less likely to end up in hospital.
Researchers have found that omicron multiplies 70 times faster in the airways than delta yet replicates 10 times more slowly in the lungs, which may explain why it is very transmissible but less severe.
Imperial College has also found that people with omicron were up to 20 per cent less likely to be hospitalised and up to 45 per cent less likely to need a hospital stay of one or more nights.
Commenting on the new research Paul Hunter, Professor of Medicine at the University of East Anglia said: “If you have recently had delta infection then you are a bit less likely to get infected by omicron though rather more reduced risk of getting severe disease.
“It also works the other way around once you have omicron you are a bit less likely to get infected by delta but with a rather more reduced risk of getting severe disease.”