Re-infection Risk May Be Higher With Omicron Variant

(Reuters) – Survivors of previous infection with the virus that causes COVID-19 may be at higher risk for re-infection with the Omicron variant than with earlier versions of the virus, according to preliminary findings.

In South Africa, where Omicron was first reported, researchers reviewed data on nearly 2.8 million infections and saw that while the risk of a first infection rose when the earlier Beta and Delta variants spread during the pandemic’s second and third waves, the risk of re-infection was low and did not change. But last month, as Omicron spread, daily numbers of re-infections spiked, the researchers reported on medRxiv ahead of peer review.

Survivors’ risk for re-infection may be rising more quickly than an average person’s risk for a first infection, they said.

SARS-CoV-2 infections are usually diagnosed without genetic sequencing to confirm the responsible variant, so this study cannot prove that Omicron is better able to evade the immune defenses put up by the body in response to a previous infection. Nor does it prove anything about defenses generated by vaccination.

Still, the researchers said, the timing of the increase in re-infections “strongly suggests that they are driven by the emergence of the Omicron variant.”

SOURCE: medRxiv, online December 2, 2021.

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