Omicron could displace Delta by boosting immunity against the variant, a small study suggests

• Infection with the Omicron variant of the coronavirus appears to enhance immunity against Delta, a small South African study found.
• This was especially the case among vaccinated people, the research, involving 13 participants, found.

Infection with the Omicron variant of the coronavirus may enhance immunity against the Delta variant, especially in vaccinated people, a small study by scientists in South Africa, published Tuesday, has found.

Scientists from the Africa Health Research Institute (AHRI) suggested that based on their research, Omicron could displace Delta because people infected with Omicron were less likely to be re-infected with Delta.

Omicron cases are surging and it's become dominant coronavirus strain in the US. Studies suggest that Omicron is more transmissible than previous variants and is capable of evading immunity provided by vaccines and prior infection. Some data indicates its symptoms are milder.

The AHRI study has been submitted as a pre-print and hasn't been peer-reviewed. It involved 13 vaccinated and unvaccinated participants. Of the 13 participants, seven were vaccinated, including one who had received a booster shot.

The scientists measured how well participants were able to neutralize Omicron and Delta upon enrollment into the study, and then 14 days later. They found that Omicron neutralization rose 14-fold during this time and Delta neutralization increased 4.4-fold.

Vaccinated participants "were able to mount a better neutralizing response against Delta" while the response in unvaccinated participants was "more variable," the paper says.

"The increase in Delta variant neutralization in individuals infected with Omicron may result in decreased ability of Delta to re-infect those individuals," Alex Sigal, the lead author of the study, said.

He added: "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."

The scientists said that because participants were likely previously infected with COVID-19, and more than half were vaccinated, it was unclear whether the results were caused by cross-neutralization of the Delta virus by Omicron-elicited antibodies, or by activating an antibody immunity from previous infection or vaccination.

South Africa first reported the Omicron variant to the World Health Organization on November 24.