Infection with Omicron may reduce risk from Delta variant too, shows study

Infection with the omicron coronavirus variant can also strengthen immunity against the earlier delta strain, reducing the risk of severe disease, according to a paper released by South African scientists.

While omicron has been shown to be highly transmissible and can evade some antibodies, after two weeks of getting symptoms immunity to subsequent infections from the strain rose 14-fold, according to the authors led by Alex Sigal and Khadija Khan of the Durban, South Africa-based Africa Health Research Institute. A smaller improvement was found against delta, they said.

“If we are lucky, omicron is less pathogenic, and this immunity will help push delta out,” said Sigal, who has previously found a two-dose course of Pfizer Inc. and BioNTech SE’s Covid-19 shot as well as a previous infection may give stronger protection against omicron.

The latest findings suggest the likelihood of someone infected with omicron being reinfected by delta is limited, reducing the presence of the latter strain. Omicron is the dominant variant in South Africa’s fourth wave of infections, delivering record case numbers, and is fast becoming the dominant strain globally.

Delta ripped through the country in July and August, leading to record hospitalization figures. Omicron hasn’t yet had such an impact on health services.

The study is based on 15 participants, of which two were excluded as they didn’t detectably neutralize omicron, and the data are being submitted to MedRxiv, a preprint medical publication. It has not been peer reviewed.