Clinical Severity of SARS-CoV-2 Variants during COVID-19 Vaccination: A Systematic Review and Meta-Analysis

Due to the variation in the SARS-CoV-2 virus, COVID-19 exhibits significant variability in severity. This presents challenges for governments in managing the allocation of healthcare resources and prioritizing health interventions. Clinical severity is also a critical statistical parameter for researchers to quantify the risks of infectious disease, model the transmission of COVID-19, and provide targeted measures to control the pandemic. To obtain more accurate severity estimates—confirmed case-hospitalization risk (cCHR), confirmed case-fatality risk (cCFR), hospitalization-fatality risk (HFR), and hospitalization-ICU risk (HIR)—we conducted a systematic review and meta-analysis on the clinical severity of different variants during the period of COVID-19 mass vaccination and provided pooled estimates for each metric. Searches were conducted on 1 February 2022 in PubMed for articles published from 1 January 2020 to 1 February 2022. Of 3536 studies identified, 13 met inclusion criteria. Pooled results show that the Delta and Omicron variants have the highest (6.56%, 0.46%, 9.06%, and 19.63%) and lowest severities (1.51%, 0.04%, 3.18%, and 6.01%), respectively, across the four metrics. Adults over 65 have higher severity levels for all metrics.

Zhilu Yuan, Zengyang Shao, Lijia Ma, Renzhong Guo