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. 2023 Apr 14:14:1051104.
doi: 10.3389/fmicb.2023.1051104. eCollection 2023.

Elder and booster vaccination associates with decreased risk of serious clinical outcomes in comparison of Omicron and Delta variant: A meta-analysis of SARS-CoV-2 infection

Yanhua Wu  1   2 , Yuchen Pan  1   2 , Kaisheng Su  2 , Yangyu Zhang  1   2 , Zhifang Jia  1   2 , Jiaxin Yi  2 , Haiyong Lv  2 , Lihuan Zhang  3 , Mingyang Xue  4 , Donghui Cao  2 , Jing Jiang  1   2
Affiliations

Elder and booster vaccination associates with decreased risk of serious clinical outcomes in comparison of Omicron and Delta variant: A meta-analysis of SARS-CoV-2 infection

Yanhua Wu et al. Front Microbiol. .

Abstract

Background: The COVID-19 pandemic brings great pressure to the public health systems. This meta-analysis aimed to compare the clinical outcomes among different virus variants, to clarify their impact on medical resources and to provide evidence for the formulation of epidemic prevention policies.

Methods: A systematic literature search was performed in the PubMed, Embase, and Cochrane Library databases using the key words "Omicron" and "Delta." The adjusted Risk ratios (RRs), Odds ratios (ORs) and Hazard ratios (HRs) were extracted, and RRs and Rate difference % (RD%) were used to interpret the risk estimates of the outcomes ultimately.

Results: Forty-three studies were included, with 3,812,681 and 14,926,841 individuals infected with SARS-CoV-2 Delta and Omicron variant, respectively. The relative risks of hospitalization, death, ICU admission, and mechanical ventilation use after infection with the Omicron variant were all significantly reduced compared those after infection with the Delta variant (RRhospitalization = 0.45, 95%CI: 0.40-0.52; RRdeath = 0.37, 95%CI: 0.30-0.45; RRICU = 0.35, 95%CI: 0.29-0.42; RRmechanical ventilation = 0.33, 95%CI: 0.25-0.44). The change of both absolute and relative risks for hospitalization was more evident (RR = 0.47, 95%CI: 0.42-0.53；RD% =10.61, 95%CI: 8.64-12.59) and a significant increase was observed for the absolute differences in death in the elderly (RD% = 5.60, 95CI%: 4.65-6.55); the change of the absolute differences in the risk of hospitalization and death were most markedly observed in the patients with booster vaccination (RD%hospitalization = 8.60, 95CI%: 5.95-11.24; RD%death = 3.70, 95CI%: 0.34-7.06).

Conclusion: The ability of the Omicron variant to cause severe clinical events has decreased significantly, as compared with the Delta variant, but vulnerable populations still need to be vigilant. There was no interaction between the vaccination doses and different variants.

Keywords: Delta; Omicron; SARS-CoV-2; clinical outcome; meta-analysis.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) 2020 flow diagram of study selection and data extraction.
Figure 2
Figure 2
The forest plots of risk of hospitalization, death, intensive care unit (ICU) admission, and mechanical ventilation (Omicron vs. Delta). (A) Risk ratio of hospitalization. (B) Risk ratio of death. (C) Risk ratio of ICU admission. (D) Risk ratio of mechanical ventilation.
Figure 3
Figure 3
The forest plots of subgroups stratified by vaccination status (Omicron vs. Delta). (A) Risk ratio of hospitalization. (B) Risk ratio of death.
See this image and copyright information in PMC

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