Department of Environmental and Prevention Sciences, University of Ferrara, Ferrara, Italy.
Local Health Unit of Pescara, Pescara, Italy.
Front Public Health. 2022 May 2;10:884121. doi: 10.3389/fpubh.2022.884121. eCollection 2022.
Current data suggest that SARS-CoV-2 reinfections are rare. Uncertainties remain, however, on the duration of the natural immunity, its protection against Omicron variant, and on the impact of vaccination to reduce reinfection rates. In this retrospective cohort analysis of the entire population of an Italian region, we followed 1,293,941 subjects from the beginning of the pandemic to the current scenario of Omicron predominance (up to mid-February 2022). After an average of 277 days, we recorded 729 reinfections among 119,266 previously infected subjects (overall rate: 6.1‰), eight COVID-19-related hospitalizations (7/100,000), and two deaths. Importantly, the incidence of reinfection did not vary substantially over time: after 18-22 months from the primary infection, the reinfection rate was still 6.7‰, suggesting that protection conferred by natural immunity may last beyond 12 months. The risk of reinfection was significantly higher among females, unvaccinated subjects, and during the Omicron wave.
现有数据表明，SARS-CoV-2 再感染较为罕见。然而，自然免疫的持续时间、其对奥密克戎变异株的保护作用，以及接种疫苗降低再感染率的效果仍存在不确定性。在这项对意大利某一地区全部人群进行的回顾性队列分析中，我们自疫情开始至奥密克戎流行时期（截至 2022 年 2 月中旬）对 1293941 名受试者进行了随访。在平均 277 天后，我们在 119266 名既往感染者中记录到 729 例再感染（总发生率：6.1‰）、8 例与 COVID-19 相关的住院治疗（7/10 万）和 2 例死亡。重要的是，再感染的发生率随时间变化不大：初次感染后 18-22 个月，再感染率仍为 6.7‰，表明自然免疫提供的保护作用可能持续 12 个月以上。女性、未接种疫苗者以及在奥密克戎流行期间，再感染的风险显著更高。
