The Omicron variant has been linked to a substantial rise in coronavirus reinfections in South Africa compared with previous waves, according to the first detailed study into the heavily mutated strain that has sparked global alarm.
“Analysis of routine surveillance data from South Africa suggests that, in contrast to the Beta and Delta [variants], the Omicron variant of Sars-Cov-2 demonstrates substantial population-level evidence for evasion of immunity from prior infection,” South African epidemiologists concluded in the study published late on Thursday.
Higher reinfections detected recently were “consistent with the timing of the emergence of the Omicron variant in South Africa”, they added.
The study did not examine Omicron’s effects on vaccine-induced immunity or examine whether the reinfected cases were more likely to become severely ill.
The findings by South Africa’s National Institute For Communicable Diseases, the public health body, will alarm global health experts who have been watching the surge in cases linked to Omicron, amid fears that its unusual genetic make-up could allow it to evade immune protection from prior infection or vaccination.
Based on analysis of test results recorded up to November 27, the study — yet to be peer-reviewed — looked at people who were first infected at least three months earlier. It compared the risk of reinfection during the first wave of the pandemic with subsequent waves of different variants.
While either the Beta or Delta waves were not associated with an elevated risk of reinfection, the risk of reinfection from Omicron was 2.4 times higher, the scientists concluded. Prior infection was previously estimated to provide at least an 80 per cent reduction in infection risk.