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A new preprint article from South Africa suggests that the novel coronavirus variant Omicron is more likely to cause infection in those who have already been infected with a prior strain of the SARS-CoV-2 virus. The study, “Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa” used data from 2,796,982 individuals with laboratory-confirmed SARS-CoV-2 who had a positive test result at least 90 days prior to 27 November 2021.

The pre-print data suggest that Omicron may be 3 times more transmissible in those with prior infection compared to the Delta strain. The authors conclude that this evidence points to the fact that the Omicron variant may have “substantial ability to evade immunity from prior infection”. Dr. Jeremy Luban, a virologist at the University of Massachusetts Medical School has said that Omicron may be more transmissible than Delta, however, “nobody knows. The problem is that our data is very limited.” Much about the changing nature of this particular virus is still very much in its infancy and it is unclear whether vaccines will offer benefits to new strains going forward. While the article has yet to undergo peer-review, if the data are robust, it points out that the “Omicron variant has been associated with a decrease in the hazard coefficient for primary infection and an increase in reinfection hazard coefficient”. It appears at this time that Omicron is more transmissible only among those who have already been infected. This may have a different impact on the international spread compared to prior variants.

Source: Juliet R.C. et al, ‘Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa’ [Pre-print]

https://doi.org/10.1101/2021.11.11.21266068