Previous SARS-CoV-2 infections and their impact on the protection from reinfection during the Omicron BA.5 wave - a nested case-control study among vaccinated adults in Sweden.

Kahn F, Bonander C, Moghaddassi M, Christiansen CB, Bennet L, Malmqvist U, Inghammar M, Björk J

IJID Reg 10 (-) 235-239 [2024-03-00; online 2024-02-28]

We evaluated the protection afforded by SARS-CoV-2 infection-induced immunity against reinfection among working-age vaccinated individuals during a calendar period from June to December 2022 when Omicron BA.5 was the dominating subvariant in Scania County, Sweden. The study cohort (n = 71,592) mainly consisted of health care workers. We analyzed 4144 infected cases during the Omicron BA.5 dominance and 41,440 sex- and age-matched controls with conditional logistic regression. The average protection against reinfection was marginal (16%, 95% confidence interval [CI] 7-23%) during the study period but substantially higher for recent infections. Recent infection (3-6 months) with Omicron BA.2 and BA.5 offered strong protection (86%, 95% CI 68-94% and 78%, 95% CI 69-84%), whereas more distant infection (6-12 months) with Omicron BA.1, BA.2, and the variants before Omicron offered marginal or no protection. These findings suggest that infection-induced immunity contributes to short-term population protection against infection with the subvariant BA.5 among working-age vaccinated individuals but wanes considerably with time, independent of the virus variant.

Category: Health

Category: Omicron VoC

Funder: Forte

Funder: VR

Funder: Vinnova

Type: Journal article

PubMed 38532742

DOI 10.1016/j.ijregi.2024.02.004

Crossref 10.1016/j.ijregi.2024.02.004

pmc: PMC10964055
pii: S2772-7076(24)00014-6

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