Tan Sophia T, Rodríguez-Barraquer Isabel, Kwan Ada T, Blumberg Seth, Park Hailey J, Hutchinson Justine, Leidner David, Lewnard Joseph A, Sears David, Lo Nathan C
medRxiv. 2024 Oct 9:2024.07.23.24310889. doi: 10.1101/2024.07.23.24310889.
Early investigation revealed that COVID-19 vaccines confer indirect protection to fully susceptible and unvaccinated persons, defined as a reduced risk of SARS-CoV-2 infection among social contacts of vaccinated individuals. However, indirect protection from infection-acquired immunity and its comparative strength and durability to vaccine-derived indirect protection in the current epidemiologic context of high levels of vaccination, prior infection, and novel variants are not well characterized. Here, we show that both infection-acquired and vaccine-derived immunity independently yield indirect protection to close social contacts with key differences in their strength and waning. Analyzing anonymized data from a system-wide SARS-CoV-2 surveillance program of 177,319 residents across 35 California state prisons from December 2021 to December 2022 in a case-control design, we find that vaccine-derived indirect protection against Omicron SARS-CoV-2 infection is strongest within three months post-vaccination [30% (95% confidence interval: 20-38%)] with subsequent modest protection, whereas infection-acquired immunity provides 38% (24-50%) indirect protection to roommates for 6 months after SARS-CoV-2 infection, with moderate indirect protection persisting for over one year. Variant-targeted vaccines (bivalent formulation including Omicron subvariants BA.4/BA.5) confer strong indirect protection for at least three months [40% (3-63%)]. These results have important implications for understanding the long-term transmission dynamics of SARS-CoV-2 and can guide vaccine policy and public health measures, especially in high-risk environments such as prisons.
早期调查显示，新冠病毒疫苗可为完全易感且未接种疫苗的人群提供间接保护，这种间接保护定义为接种疫苗者的社会接触者感染严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的风险降低。然而，在当前疫苗接种率高、既往感染率高以及出现新变种的流行病学背景下，感染获得性免疫的间接保护及其与疫苗衍生间接保护的相对强度和持久性尚未得到充分表征。在此，我们表明，感染获得性免疫和疫苗衍生免疫均能独立地为密切社会接触者提供间接保护，但其强度和减弱情况存在关键差异。在一项病例对照设计中，我们分析了2021年12月至2022年12月加利福尼亚州35所监狱中177319名居民的全系统SARS-CoV-2监测项目的匿名数据，发现疫苗衍生的针对奥密克戎SARS-CoV-2感染的间接保护在接种疫苗后三个月内最强[30%（95%置信区间：20 - 38%）]，随后保护作用适度减弱，而感染获得性免疫在SARS-CoV-2感染后6个月为室友提供38%（24 - 50%）的间接保护，中度间接保护持续一年以上。针对变种的疫苗（包括奥密克戎亚型BA.4/BA.5的二价制剂）可提供至少三个月的强烈间接保护[40%（3 - 63%）]。这些结果对于理解SARS-CoV-2的长期传播动态具有重要意义，并可指导疫苗政策和公共卫生措施，尤其是在监狱等高风险环境中。
