BC Centre for Disease Control, Vancouver, BC, Canada.
University of British Columbia Centre for Disease Control, Vancouver, BC, Canada.
JMIR Public Health Surveill. 2024 Aug 27;10:e45513. doi: 10.2196/45513.
SARS-CoV-2 variants of concern (VOCs) emerged and rapidly replaced the original strain worldwide. The increased transmissibility of these new variants led to increases in infections, hospitalizations, and mortality. However, there is a scarcity of retrospective investigations examining the severity of all the main VOCs in presence of key public health measures and within various social determinants of health (SDOHs).
This study aims to provide a retrospective assessment of the clinical severity of COVID-19 VOCs in the context of heterogenous SDOHs and vaccination rollout.
We used a population-based retrospective cohort design with data from the British Columbia COVID-19 Cohort, a linked provincial surveillance platform. To assess the relative severity (hospitalizations, intensive care unit [ICU] admissions, and deaths) of Gamma, Delta, and Omicron infections during 2021 relative to Alpha, we used inverse probability treatment weighted Cox proportional hazard modeling. We also conducted a subanalysis among unvaccinated individuals, as assessed severity differed across VOCs and SDOHs.
We included 91,964 individuals infected with a SARS-CoV-2 VOC (Alpha: n=20,487, 22.28%; Gamma: n=15,223, 16.55%; Delta: n=49,161, 53.46%; and Omicron: n=7093, 7.71%). Delta was associated with the most severe disease in terms of hospitalization, ICU admissions, and deaths (hospitalization: adjusted hazard ratio [aHR] 2.00, 95% CI 1.92-2.08; ICU: aHR 2.05, 95% CI 1.91-2.20; death: aHR 3.70, 95% CI 3.23-4.25 relative to Alpha), followed generally by Gamma and then Omicron and Alpha. The relative severity by VOC remained similar in the unvaccinated individual subanalysis, although the proportion of individuals infected with Delta and Omicron who were hospitalized was 2 times higher in those unvaccinated than in those fully vaccinated. Regarding SDOHs, the proportion of hospitalized individuals was higher in areas with lower income across all VOCs, whereas among Alpha and Gamma infections, 2 VOCs that cocirculated, differential distributions of hospitalizations were found among racially minoritized groups.
Our study provides robust severity estimates for all VOCs during the COVID-19 pandemic in British Columbia, Canada. Relative to Alpha, we found Delta to be the most severe, followed by Gamma and Omicron. This study highlights the importance of targeted testing and sequencing to ensure timely detection and accurate estimation of severity in emerging variants. It further sheds light on the importance of vaccination coverage and SDOHs in the context of pandemic preparedness to support the prioritization of allocation for resource-constrained or minoritized groups.
引起关注的 SARS-CoV-2 变体（VOC）出现并在全球范围内迅速取代了原始毒株。这些新变体的传染性增加导致感染、住院和死亡人数增加。然而，对于所有主要 VOC 在存在关键公共卫生措施和各种健康社会决定因素 (SDOH) 时的严重程度，缺乏回顾性调查。
本研究旨在提供 COVID-19 VOC 在异质 SDOH 和疫苗接种实施背景下的临床严重程度的回顾性评估。
我们使用基于人群的回顾性队列设计，利用不列颠哥伦比亚 COVID-19 队列的数据，这是一个省级监测平台。为了评估 2021 年与 Alpha 相比，Gamma、Delta 和 Omicron 感染的相对严重程度（住院、重症监护病房 [ICU] 入院和死亡），我们使用逆概率治疗加权 Cox 比例风险建模。我们还在未接种疫苗的个体中进行了亚分析，因为 VOC 和 SDOH 之间的严重程度评估有所不同。
我们纳入了 91964 名感染 SARS-CoV-2 VOC 的个体（Alpha：n=20487，22.28%；Gamma：n=15223，16.55%；Delta：n=49161，53.46%；Omicron：n=7093，7.71%）。Delta 与住院、ICU 入院和死亡的最严重疾病相关（住院：调整后的危险比[aHR]2.00，95%CI 1.92-2.08；ICU：aHR 2.05，95%CI 1.91-2.20；死亡：aHR 3.70，95%CI 3.23-4.25 相对于 Alpha），其次是 Gamma，然后是 Omicron 和 Alpha。在未接种疫苗的个体亚分析中，VOC 的相对严重程度仍然相似，尽管未接种疫苗的个体感染 Delta 和 Omicron 而住院的比例是完全接种疫苗的个体的 2 倍。关于 SDOH，所有 VOC 中，收入较低地区的住院人数比例较高，而在 Alpha 和 Gamma 感染中，作为同时流行的 2 个 VOC，在少数族裔群体中发现了住院分布的差异。
我们的研究在加拿大不列颠哥伦比亚省 COVID-19 大流行期间为所有 VOC 提供了可靠的严重程度估计。与 Alpha 相比，我们发现 Delta 是最严重的，其次是 Gamma 和 Omicron。本研究强调了靶向检测和测序的重要性，以确保及时发现和准确估计新出现变体的严重程度。它进一步阐明了疫苗接种覆盖率和 SDOH 在大流行准备中的重要性，以支持为资源有限或少数群体的优先分配提供支持。
