Abstract
With the continuation of the pandemic, many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have appeared around the world. Owing to a possible risk of increasing the transmissibility of the virus, severity of the infected individuals, and the ability to escape the antibody produced by the vaccines, the four SARS-CoV-2 variants of Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2) have attracted the most widespread attention. At present, there is a unified conclusion that these four variants have increased the transmissibility of SARS-CoV-2, but the severity of the disease caused by them has not yet been determined. Studies from June 1, 2020 to October 15, 2021 were considered, and a meta-analysis was carried out to process the data. Alpha, Beta, Gamma, and Delta variants are all more serious than the wild-type virus in terms of hospitalization, ICU admission, and mortality, and the Beta and Delta variants have a higher risk than the Alpha and Gamma variants. Notably, the random effects of Beta variant to the wild-type virus with respect to hospitalization rate, severe illness rate, and mortality rate are 2.16 (95% CI: 1.19–3.14), 2.23 (95% CI: 1.31–3.15), and 1.50 (95% CI: 1.26–1.74), respectively, and the random effects of Delta variant to the wild-type virus are 2.08 (95% CI: 1.77–2.39), 3.35 (95% CI: 2.5–4.2), and 2.33 (95% CI: 1.45–3.21), respectively. Although, the emergence of vaccines may reduce the threat posed by SARS-CoV-2 variants, these are still very important, especially the Beta and Delta variants.
Highlights
There are multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants identified by viral genomic sequencing in different parts of the world
This study is a systematic review of current evidence conducted in June 2021 to determine the effects of SARS-CoV-2 VOCs on disease severity and clinical outcomes
We identified a total of 1,745 (1,076, PubMed; 448, MEDLINE; 183, Embase; and 38 from other sources) relevant articles, and 1,123 studies were left after removing the duplicates
Summary
There are multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants identified by viral genomic sequencing in different parts of the world. Four variants have been defined as VOCs—Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2). In late December 2020, the Alpha variant was reported in the United Kingdom [1], followed quickly by the detection of the Beta variant, which carried three mutations including K417N, E484K, and N501Y at important locations in the Spike protein receptor-binding domain (S-RBD) in South Africa [2]. In early January 2021, the Gamma variant carrying three mutations consist of SARS-CoV-2 Variants of Concern. In December 2020, the Delta variant carrying mutations called 452R and 478K was first isolated in India [4]
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