Natural infection with SARS-CoV-2 has been shown to elicit strong protection against serious illness caused by the alpha, beta, and delta variants. To determine the extent to which natural infection protects against COVID-19 caused by the omicron variant, researchers in Qatar examined protection during a recent omicron outbreak (Altarawneh HN, Chemaitelly H, Hasan MR, et al. Protection Against Omicron Variant from Previous SARS-CoV-2 Infection. N Engl J Med. 2022 Feb 9).

The effectiveness of previous infection on protection against all symptomatic illness was estimated to be 90% against the alpha variant, 85.7% against the beta variant, 92% against the delta variant, and 56% against the omicron variant. Protection afforded by natural infection against severe, critical, or fatal COVID-19 was estimated to be 69.4% against the alpha variant, 88% against the beta variant, 100% against the delta variant, and 88% against the omicron variant.

These data are consistent with the finding that previous infection or vaccination is highly protective against severe disease caused by omicron, but less protective against mild disease caused by the variant.

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