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

作者：Fredrik Kahn, Carl Bonander, Mahnaz Moghaddassi, Claus Bohn Christiansen, Louise Bennet, Ulf Malmqvist, Malin Inghammar, Jonas Björk · 发表于：IJID Regions · 年份：2024 · DOI：10.1016/j.ijregi.2024.02.004 · 被引用次数：8 · 研究领域：SARS-CoV-2 and COVID-19 Research、Infection Control and Ventilation、COVID-19 epidemiological studies

Objectives: 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. Methods: 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. Results: 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. Conclusions: 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.