Omicron variant infection confers enhanced immunity to Delta

A study by South African scientists suggests that Omicron may replace the Delta variant of the coronavirus because infection with the new variant boosts immunity to the old one.
The study involved only a small group of people and was not peer-reviewed, but it found that people infected with Omicron, particularly those who were vaccinated, developed enhanced immunity to the Delta variant.
The analysis included 33 vaccinated and unvaccinated individuals who were infected with the Omicron variant in South Africa.
While the authors found that Omicron variant neutralization increased 14-fold within 14 days of enrollment, they also found that Delta variant neutralization increased 4.4-fold.
“Increased neutralization of the Delta variant in Omicron-infected individuals may lead to a decrease in the ability of Delta to reinfect these individuals,” said the scientists who conducted the study.
The study results are “consistent with Omicron displacing the Delta variant, as it may elicit immunity that neutralizes Delta, making reinfection with Delta less likely,” they added.
The implications of this displacement depend on whether Omicron is less pathogenic than Delta, the scientists said. “If it is, then the incidence of severe COVID-19 disease would be reduced and the infection could shift to become less disruptive to individuals and society.”
Alex Sigal, a professor at the Africa Health Research Institute in South Africa, said Monday on Twitter that if Omicron is less pathogenic, as it appeared to be from the South African experiment, “it will help push Delta out.”