Departamento de Epidemiologia. Instituto Nacional de Saúde Doutor Ricardo Jorge. Lisboa. Portugal.
Departamento de Doenças Infeciosas. Instituto Nacional de Saúde Doutor Ricardo Jorge. Lisboa. Portugal.
Acta Med Port. 2021 Feb 1;34(2):87-94. doi: 10.20344/amp.15122.
The aim of this study was to estimate and describe the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibodies (immunoglobulin M and/or immunoglobulin G) in Portugal in May-July 2020.
A cross-sectional seroepidemiological survey was developed after the peak of the first epidemic wave on a sample of 2301 Portuguese residents, aged 1 year or older. Survey sample was selected using a two-stage stratified non-probability sampling design (quota sampling). SARS-CoV-2 immunoglobulin M and immunoglobulin G antibodies were measured in serum samples by enzyme-linked immunosorbent assay. Seroprevalence estimates of immunoglobulin M and/or immunoglobulin G and 95% confidence intervals were stratified by sex, age group, health region and education.
Overall, seroprevalence was 2.9% (95% confidence interval: 2.0% - 4.2%). Higher prevalence rates were observed in male (4.1%, 95% confidence interval: 2.6% - 6.6%) and those with secondary education (6.4%, 95% confidence interval: 3.2% - 12.5%). Differences in seroprevalence by age group and region were not statistically significant.
The estimated seroprevalence of SARS-CoV-2 was higher than the cumulative incidence reported by the National Surveillance System but far from necessary to reach herd immunity.
Our results support limited extent of infection by SARS-CoV-2 in the study population possibly due to early lockdown measures implemented in Portugal and support the need to continue monitoring of SARS-CoV-2 seroprevalence in order to increase our knowledge about the evolution of the epidemic and to estimate the proportion of the susceptible population over time.
本研究旨在估计和描述 2020 年 5 月至 7 月葡萄牙严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）特异性抗体（免疫球蛋白 M 和/或免疫球蛋白 G）的流行情况。
在第一次疫情高峰过后，对 2301 名年龄在 1 岁及以上的葡萄牙居民进行了横断面血清流行病学调查。使用两阶段分层非概率抽样设计（配额抽样）选择调查样本。通过酶联免疫吸附试验测量血清样本中的 SARS-CoV-2 免疫球蛋白 M 和免疫球蛋白 G 抗体。对免疫球蛋白 M 和/或免疫球蛋白 G 的血清阳性率估计值及其 95%置信区间按性别、年龄组、卫生区和教育程度进行分层。
总体而言，血清阳性率为 2.9%（95%置信区间：2.0%-4.2%）。男性（4.1%，95%置信区间：2.6%-6.6%）和接受过中等教育（6.4%，95%置信区间：3.2%-12.5%）的人群观察到更高的阳性率。按年龄组和地区划分的血清阳性率差异无统计学意义。
估计的 SARS-CoV-2 血清阳性率高于国家监测系统报告的累计发病率，但远未达到群体免疫所需的水平。
我们的结果支持 SARS-CoV-2 在研究人群中的感染程度有限，这可能是由于葡萄牙早期实施的封锁措施，支持继续监测 SARS-CoV-2 的血清阳性率，以增加我们对疫情演变的了解，并估计随时间推移易感人群的比例。
