Department of Microbiology, Faculty of Medicine, University of Peradeniya, Peradeniya, 20400, Sri Lanka.
Office of the Regional Director of Health Services, Kandy, Sri Lanka.
BMC Public Health. 2022 Oct 25;22(1):1961. doi: 10.1186/s12889-022-14381-5.
Asymptomatic SARS-CoV-2 infection occurring in RT-PCR negative individuals represent a poorly characterized cohort with important infection control connotations. While household and community-based studies have evaluated seroprevalence of antibody and transmission dynamics in this group, workplace-based data is currently unavailable.
A cohort study was carried out in July 2021, during and immediately following the peak of the 3 wave of COVID-19 in Sri Lanka, prior to mass vaccination. A total of 92 unvaccinated individuals between the ages of 17-65 years were purposively sampled from an office and two factory settings. The selected cohort that had been exposed to RT-PCR positive cases in the workplace was tested RT-PCR negative. Serological samples collected six weeks post exposure were tested for anti-SARS-CoV-2 neutralizing antibody.
The seroprevalence for SARS-CoV-2 specific neutralizing antibodies in the overall cohort was 63.04% (58/92). Seroprevalences in the office setting, factory setting 1 and factory setting 2 were 69.2% (9/13), 55.7% (34/61) and 83.33% (15/18), respectively. Primary risk factor associated with seropositivity was face to face contact with no mask for > 15 min (p < 0.024, Odds Ratio (OR); 5.58, 95%CI;1.292- 25.65). Individuals with workspace exposure had significantly higher levels of neutralizing antibodies than those who did not (percentage neutralization in assay 63.3% (SD:21)vs 45.7% (SD:20), p = 0.0042), as did individuals who engaged socially without protective measures (62.4 (SD:21.6)% vs 49.7 (SD:21)%, p = 0.026).
There was a high seroprevalence for SARS-CoV-2 specific neutralizing antibodies among RT-PCR negative contacts in workplace settings in Sri Lanka. Higher levels of transmission of SARS-CoV-2 infection than estimated based on RT-PCR positive contact data indicate need for targeted infection control measures in these settings during future outbreaks.
在 RT-PCR 检测结果为阴性的个体中出现无症状的 SARS-CoV-2 感染，这代表了一个特征描述较差的群体，具有重要的感染控制含义。虽然家庭和社区研究已经评估了该群体中的抗体血清阳性率和传播动态，但目前尚无基于工作场所的数据。
在 2021 年 7 月，斯里兰卡 COVID-19 第三波疫情高峰期间和之后立即进行了一项队列研究，当时尚未大规模接种疫苗。从一个办公室和两个工厂中，有目的地选择了年龄在 17-65 岁之间的 92 名未接种疫苗的个体。在工作场所接触过 RT-PCR 阳性病例的选定队列中，检测结果均为 RT-PCR 阴性。在接触后 6 周采集血清样本，检测针对 SARS-CoV-2 的中和抗体。
总体队列中 SARS-CoV-2 特异性中和抗体的血清阳性率为 63.04%（58/92）。在办公室、工厂 1 和工厂 2 中，血清阳性率分别为 69.2%（9/13）、55.7%（34/61）和 83.33%（15/18）。与血清阳性相关的主要危险因素是面对面接触且未戴口罩超过 15 分钟（p<0.024，优势比（OR）；5.58，95%置信区间；1.292-25.65）。与未暴露于工作场所的个体相比，暴露于工作场所的个体具有更高水平的中和抗体（在检测中中和抗体的百分比分别为 63.3%（SD：21）和 45.7%（SD：20），p=0.0042），并且与未采取保护措施进行社交的个体相比，其水平更高（62.4%（SD：21.6）%和 49.7%（SD：21）%，p=0.026）。
在斯里兰卡工作场所的 RT-PCR 检测结果为阴性的接触者中，SARS-CoV-2 特异性中和抗体的血清阳性率较高。SARS-CoV-2 感染的传播水平高于基于 RT-PCR 阳性接触者数据的估计，这表明在未来的疫情中，需要在这些环境中采取有针对性的感染控制措施。
