丹麦哥本哈根大学Steen Ethelberg团队评估了2020年丹麦400万PCR检测个体对SARS-CoV-2再感染的防护能力。2021年3月17日，该成果发表在《柳叶刀》杂志上。
SARS-CoV-2感染对随后再感染的保护程度尚不清楚。2020年，作为丹麦广泛的免费PCR检测战略的一部分，大约400万人（占人口的69%）接受了1060万次检测。利用这些2020年的PCR检测数据，研究组估计了针对SARS-CoV-2重复感染的保护作用。
在这项人群层面观察性研究中，研究组从丹麦微生物学数据库中收集了2020年在丹麦接受检测的患者的个体层面数据，分析了从2020年9月1日至12月31日COVID-19第二波疫情期间的感染率，并与第一波疫情期间（2020年3月至5月）PCR检测阳性和阴性个体之间的感染率进行比较。在主要分析中，研究组排除了在两波疫情之间第一次检测呈阳性的个体和在第二波疫情之前死亡的个体。研究组还做了一个替代队列分析，比较了至少3个月前有和没有确诊感染的人全年的感染率，而不考虑日期，并调查年龄组、性别和感染后时间是否存在差异。
在第一波疫情期间（即2020年6月之前），共检测533 381人，其中11 727人（2.20%）为PCR阳性，第二波疫情期间有525 339人符合随访条件，其中11 068人（2.11%）在第一波疫情期间检测为阳性。在第一波疫情后符合资格的PCR阳性个体中，72人（0.65%）在第二波疫情爆发后再次呈阳性，而在第一波疫情爆发后呈阴性的514 271人中有16 819人（3.27%）在第二波疫情后呈阳性。
针对重复感染的保护率为80.5%。替代队列分析给出了类似的估计，估计保护率为78.8%。在替代队列分析中，65岁及以上的人群中观察到针对重复感染的保护率为47.1%。研究组未发现性别对重复感染的保护作用，其中男性为78.4%，女性为79.1%；也未发现保护作用随时间减弱的证据，随访3-6个月为79.3%，随访7个月以上为77.7%。
该研究结果可为决定哪些群体应该接种疫苗提供依据，并提倡对以前感染的人也接种疫苗，因为不能依靠天然保护（尤其是老年人）。
附：英文原文
Title: Assessment of protection against reinfection with SARS-CoV-2 among 4 million PCR-tested individuals in Denmark in 2020: a population-level observational study
Author: Christian Holm Hansen, Daniela Michlmayr, Sophie Madeleine Gubbels, Kre Mlbak, Steen Ethelberg
Issue&Volume: 2021-03-17
Abstract:
Background
The degree to which infection with SARS-CoV-2 confers protection towards subsequent reinfection is not well described. In 2020, as part of Denmark's extensive, free-of-charge PCR-testing strategy, approximately 4 million individuals (69% of the population) underwent 10·6 million tests. Using these national PCR-test data from 2020, we estimated protection towards repeat infection with SARS-CoV-2.
Methods
In this population-level observational study, we collected individual-level data on patients who had been tested in Denmark in 2020 from the Danish Microbiology Database and analysed infection rates during the second surge of the COVID-19 epidemic, from Sept 1 to Dec 31, 2020, by comparison of infection rates between individuals with positive and negative PCR tests during the first surge (March to May, 2020). For the main analysis, we excluded people who tested positive for the first time between the two surges and those who died before the second surge. We did an alternative cohort analysis, in which we compared infection rates throughout the year between those with and without a previous confirmed infection at least 3 months earlier, irrespective of date. We also investigated whether differences were found by age group, sex, and time since infection in the alternative cohort analysis. We calculated rate ratios (RRs) adjusted for potential confounders and estimated protection against repeat infection as 1–RR.
Findings
During the first surge (ie, before June, 2020), 533381 people were tested, of whom 11727 (2·20%) were PCR positive, and 525339 were eligible for follow-up in the second surge, of whom 11068 (2·11%) had tested positive during the first surge. Among eligible PCR-positive individuals from the first surge of the epidemic, 72 (0·65% [95% CI 0·51–0·82]) tested positive again during the second surge compared with 16819 (3·27% [3·22–3·32]) of 514271 who tested negative during the first surge (adjusted RR 0·195 [95% CI 0·155–0·246]). Protection against repeat infection was 80·5% (95% CI 75·4–84·5). The alternative cohort analysis gave similar estimates (adjusted RR 0·212 [0·179–0·251], estimated protection 78·8% [74·9–82·1]). In the alternative cohort analysis, among those aged 65 years and older, observed protection against repeat infection was 47·1% (95% CI 24·7–62·8). We found no difference in estimated protection against repeat infection by sex (male 78·4% [72·1–83·2] vs female 79·1% [73·9–83·3]) or evidence of waning protection over time (3–6 months of follow-up 79·3% [74·4–83·3] vs ≥7 months of follow-up 77·7% [70·9–82·9]).
Interpretation
Our findings could inform decisions on which groups should be vaccinated and advocate for vaccination of previously infected individuals because natural protection, especially among older people, cannot be relied on.
DOI: 10.1016/S0140-6736(21)00575-4
Source: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00575-4/fulltext
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本期文章：《柳叶刀》：Online/在线发表
