ABSTRACT

SARS-CoV-2 antibody seroprevalence among health-care workers (HCW) can assess past exposure and possible immunity, which varies across different regions, populations and times. We investigated the seroprevalence among HCW in Massachusetts (a region suffering high COVID-19 mortality) at the end of first wave of the SARS-CoV-2 pandemic. All HCW at Cambridge Health Alliance were invited to participate in this cross-sectional survey in June 2020. Those who volunteered, consented and provided a blood sample were included. Dried blood specimens from finger-prick sampling collected either at home by each HCW or onsite by the study team were analyzed for anti-SARS-CoV-2 IgM and IgG to the virus’ receptor binding domain, using an enzyme-linked immunosorbent assay. IgM and IgG antibody abundance were categorized based on the number of standard deviations above the cross-reacting levels found in existing, pre-pandemic blood samples previously obtained by the Ragon Institute and analyzed by the Broad Institute (Cambridge, MA). Seroprevalence estimates were made based on ‘positive’ IgM or IgG using ‘low’ (>6 SD), ‘medium’ (>4.5 SD), and ‘high’ prevalence cutoffs (>3 SD).

A total of 433 out of 5,204 eligible HCWs consented and provided samples. Participating HCWs had a lower cumulative incidence (from the start of the pandemic up to the bloodspot collections) of SARS-CoV-2 RT-PCR positivity (1.85%) compared to non-participants (3.29%). The low, medium, and high seroprevalence estimates were 8.1%, 11.3%, and 14.5%, respectively. The weighted estimates based on past PCR positivity were 13.9%, 19.4%, and 24.9%, respectively, for the entire healthcare system population after accounting for participation bias.

摘要

医护人员 (HCW) 中的 SARS-CoV-2 抗体血清阳性率可以评估过去的暴露情况和可能的免疫力，这在不同地区、人群和时间上有所不同。我们调查了第一波 SARS-CoV-2 大流行结束时马萨诸塞州（一个 COVID-19 死亡率高的地区）医护人员的血清阳性率。剑桥健康联盟的所有 HCW 都被邀请参加 2020 年 6 月的这项横断面调查。包括那些自愿、同意并提供血液样本的人。使用酶联免疫吸附测定法分析了每位医护人员在家中或研究小组现场采集的手指刺血样本的干血标本中的抗 SARS-CoV-2 IgM 和病毒受体结合域的 IgG。IgM 和 IgG 抗体丰度根据在现有的大流行前血液样本中发现的交叉反应水平之上的标准偏差数量进行分类，该样本由 Ragon 研究所先前获得并由 Broad 研究所（剑桥，马萨诸塞州）进行分析。血清阳性率估计是基于“阳性”IgM 或 IgG 使用“低”（> 6 SD）、“中”（> 4.5 SD）和“高”流行截断值（> 3 SD）进行的。

在 5,204 名符合条件的 HCW 中，共有 433 名同意并提供了样本。与非参与者 (3.29%) 相比，参与的医护人员的 SARS-CoV-2 RT-PCR 阳性累积发生率 (从大流行开始到血斑采集) (1.85%) 较低。低、中和高血清阳性率估计值分别为 8.1%、11.3% 和 14.5%。在考虑了参与偏差后，基于过去 PCR 阳性率的加权估计对于整个医疗保健系统人群分别为 13.9%、19.4% 和 24.9%。