Background

The first wave of COVID-19 in South Africa peaked in July, 2020, and a larger second wave peaked in January, 2021, in which the SARS-CoV-2 501Y.V2 (Beta) lineage predominated. We aimed to compare in-hospital mortality and other patient characteristics between the first and second waves.

Methods

In this prospective cohort study, we analysed data from the DATCOV national active surveillance system for COVID-19 admissions to hospital from March 5, 2020, to March 27, 2021. The system contained data from all hospitals in South Africa that have admitted a patient with COVID-19. We used incidence risk for admission to hospital and determined cutoff dates to define five wave periods: pre-wave 1, wave 1, post-wave 1, wave 2, and post-wave 2. We compared the characteristics of patients with COVID-19 who were admitted to hospital in wave 1 and wave 2, and risk factors for in-hospital mortality accounting for wave period using random-effect multivariable logistic regression.

Findings

Peak rates of COVID-19 cases, admissions, and in-hospital deaths in the second wave exceeded rates in the first wave: COVID-19 cases, 240·4 cases per 100 000 people vs 136·0 cases per 100 000 people; admissions, 27·9 admissions per 100 000 people vs 16·1 admissions per 100 000 people; deaths, 8·3 deaths per 100 000 people vs 3·6 deaths per 100 000 people. The weekly average growth rate in hospital admissions was 20% in wave 1 and 43% in wave 2 (ratio of growth rate in wave 2 compared with wave 1 was 1·19, 95% CI 1·18–1·20). Compared with the first wave, individuals admitted to hospital in the second wave were more likely to be age 40–64 years (adjusted odds ratio [aOR] 1·22, 95% CI 1·14–1·31), and older than 65 years (aOR 1·38, 1·25–1·52), compared with younger than 40 years; of Mixed race (aOR 1·21, 1·06–1·38) compared with White race; and admitted in the public sector (aOR 1·65, 1·41–1·92); and less likely to be Black (aOR 0·53, 0·47–0·60) and Indian (aOR 0·77, 0·66–0·91), compared with White; and have a comorbid condition (aOR 0·60, 0·55–0·67). For multivariable analysis, after adjusting for weekly COVID-19 hospital admissions, there was a 31% increased risk of in-hospital mortality in the second wave (aOR 1·31, 95% CI 1·28–1·35). In-hospital case-fatality risk increased from 17·7% in weeks of low admission (<3500 admissions) to 26·9% in weeks of very high admission (>8000 admissions; aOR 1·24, 1·17–1·32).

Interpretation

In South Africa, the second wave was associated with higher incidence of COVID-19, more rapid increase in admissions to hospital, and increased in-hospital mortality. Although some of the increased mortality can be explained by admissions in the second wave being more likely in older individuals, in the public sector, and by the increased health system pressure, a residual increase in mortality of patients admitted to hospital could be related to the new Beta lineage.

Funding

DATCOV as a national surveillance system is funded by the National Institute for Communicable Diseases and the South African National Government.

中文翻译：

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南非第一波和第二波期间因 COVID-19 入院的个体死亡率差异：一项队列研究

背景

南非的第一波 COVID-19 浪潮于 2020 年 7 月达到顶峰，第二波更大的第二波浪潮于 2021 年 1 月达到顶峰，其中 SARS-CoV-2 501Y.V2（Beta）谱系占主导地位。我们旨在比较第一波和第二波之间的住院死亡率和其他患者特征。

方法

在这项前瞻性队列研究中，我们分析了 DATCOV 国家主动监测系统中 2020 年 3 月 5 日至 2021 年 3 月 27 日住院 COVID-19 的数据。该系统包含来自南非所有收治患者的医院的数据与 COVID-19。我们使用入院的发病风险并确定截止日期来定义五个波期：前波 1、波 1、后波 1、波 2 和后波 2。我们比较了 COVID-19 患者的特征在第 1 波和第 2 波中入院的患者，以及使用随机效应多变量逻辑回归计算波期的院内死亡风险因素。

发现

第二波 COVID-19 病例、入院和院内死亡的峰值率超过了第一波：COVID-19 病例，每 10 万人 240·4 例vs每 10 万人136·0 例；入学率，每 100 000 人 27·9 次入学vs每 100 000 人16·1 次入学；死亡人数，每 100 000 人中有 8·3 人死亡vs每 100 000 人中有 3·6 人死亡。第 1 波的每周住院人数平均增长率为 20%，第 2 波为 43%（第 2 波与第 1 波的增长率比为 1·19，95% CI 1·18–1·20）。与第一波相比，第二波入院的个体更有可能年龄在 40-64 岁之间（调整后的比值比 [aOR] 1·22，95% CI 1·14-1·31），并且年龄大于65 岁 (aOR 1·38, 1·25–1·52)，与 40 岁以下相比；混血（aOR 1·21, 1·06–1·38）与白种人相比；并被公共部门录取（aOR 1·65, 1·41–1·92）；与白人相比，黑人 (aOR 0·53, 0·47–0·60) 和印度人 (aOR 0·77, 0·66-0·91) 的可能性较小；并有合并症（aOR 0·60, 0·55–0·67）。对于多变量分析，在调整每周 COVID-19 住院人数后，在第二波中，院内死亡风险增加了 31%（aOR 1·31，95% CI 1·28–1·35）。住院病死率从低入院周数（<3500 次入院）的 17·7% 增加到高入院周数（>8000 次入院；aOR 1·24, 1·17-1·）的 26·9% 32)。

解释

在南非，第二波与 COVID-19 的发病率更高、入院人数增加更快以及住院死亡率增加有关。虽然死亡率增加的部分原因可以解释为第二波中老年人、公共部门的入院率更高，以及卫生系统压力的增加，但住院患者死亡率的残余增加可能与新的 Beta 血统。

资金

DATCOV 作为国家监测系统由国家传染病研究所和南非国家政府资助。