Department of Infectious Disease Epidemiology and Prevention, Statens Serum Institut, Copenhagen, Denmark; MRC International Statistics and Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK.
Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Copenhagen, Denmark; European Programme for Public Health Microbiology Training (EUPHEM), European Centre for Disease Prevention and Control (ECDC), Solna, Sweden.
Lancet. 2021 Mar 27;397(10280):1204-1212. doi: 10.1016/S0140-6736(21)00575-4. Epub 2021 Mar 17.
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.
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.
During the first surge (ie, before June, 2020), 533 381 people were tested, of whom 11 727 (2·20%) were PCR positive, and 525 339 were eligible for follow-up in the second surge, of whom 11 068 (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 16 819 (3·27% [3·22-3·32]) of 514 271 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]).
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.
None.
SARS-CoV-2 感染赋予个体对后续再感染的保护程度尚不清楚。2020 年，作为丹麦广泛、免费 PCR 检测策略的一部分，大约有 400 万人（占人口的 69%）接受了 1060 万次检测。利用 2020 年全国的 PCR 检测数据，我们估计了 SARS-CoV-2 重复感染的保护程度。
在这项基于人群的观察性研究中，我们从丹麦微生物数据库中收集了 2020 年在丹麦接受检测的个体的个人数据，并通过比较首次激增期间（2020 年 3 月至 5 月）阳性和阴性 PCR 检测个体的感染率，分析了 2020 年 9 月 1 日至 12 月 31 日 COVID-19 疫情的第二次激增期间的感染率。（2020 年 9 月 1 日至 12 月 31 日）。对于主要分析，我们排除了两次激增之间首次检测呈阳性的人群和在第二次激增前死亡的人群。我们进行了替代队列分析，在该分析中，我们比较了至少 3 个月前有一次既往确诊感染的个体与无既往确诊感染的个体在全年的感染率，无论日期如何。我们还研究了在替代队列分析中，年龄组、性别和感染后时间是否存在差异。我们计算了调整潜在混杂因素后的调整后率比（RR），并将重复感染的保护估计为 1 - RR。
在首次激增期间（即 2020 年 6 月之前），有 533381 人接受了检测，其中 11727 人（2.20%）PCR 检测阳性，525339 人有资格在第二次激增中进行随访，其中 11068 人（2.11%）在首次激增期间检测阳性。在首次疫情激增期间 PCR 检测阳性的合格个体中，与首次激增期间检测阴性的 514271 人（32799 人，3.22%）相比，第二次激增期间再次检测阳性的有 72 人（0.65% [95%CI 0.51-0.82]）（调整 RR 0.195 [95%CI 0.155-0.246]）。重复感染的保护率为 80.5%（95%CI 75.4-84.5）。替代队列分析得出了类似的估计值（调整 RR 0.212 [0.179-0.251]，估计保护率为 78.8% [74.9-82.1]）。在替代队列分析中，65 岁及以上人群中，观察到的重复感染保护率为 47.1%（95%CI 24.7-62.8）。我们没有发现按性别（男性 78.4% [72.1-83.2]与女性 79.1% [73.9-83.3]）或随时间推移而出现保护作用减弱的证据（3-6 个月随访 79.3% [74.4-83.3]与≥7 个月随访 77.7% [70.9-82.9]）。
我们的发现可以为决定哪些人群应该接种疫苗以及提倡为既往感染者接种疫苗提供信息，因为不能依赖自然保护，尤其是老年人的自然保护。
无。
