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Review
. 2022 Jun;50(3):583-596.
doi: 10.1007/s15010-022-01759-1. Epub 2022 Feb 3.

Implication of the emergence of the delta (B.1.617.2) variants on vaccine effectiveness

Jaffar A Al-Tawfiq  1   2   3 , Thoyaja Koritala  4 , Saad Alhumaid  5 , Mazin Barry  6   7 , Abeer N Alshukairi  8 , Mohamad-Hani Temsah  9 , Abbas Al Mutair  10   11   12 , Ali Rabaan  13   14 , Raghavendra Tirupathi  15   16 , Philippe Gautret  17   18
Affiliations
Review

Implication of the emergence of the delta (B.1.617.2) variants on vaccine effectiveness

Jaffar A Al-Tawfiq et al. Infection. 2022 Jun.

Abstract

Introduction: COVID-19 vaccines have been developed to compact the current SARS-CoV-2 pandemic and have been administered to people all over the world. These vaccines have been quite effective in reducing the possibility of severe illness, hospitalization and death. However, the recent emergence of Variants of Concern specifically the delta variant, B.1.617.2, had resulted in additional waves of the pandemic.

Methods: We aim to review the literature to understand the transmission and disease severity, and determine the efficacy of the current COVID-19 vaccines. We searched Pubmed, Scopus, and Embase till August 4th 2021, and used the search terms "delta variant", "vaccinations"," breakthrough infections", and "neutralizing antibody". For the meta-analysis, 21 studies were screened in particular and five articles (148,071 cases) were included in the study, and only four were analyzed in the meta-analysis.

Results: In this review, both in vitro and in vivo studies showed significant reductions in neutralization rates against delta variants for vaccinated individuals and convalescent patients with prior history of COVID-19. However, There was a lower incidence of infection with SARS-CoV-2 due to Delta variant was found after the second dose of Pfizer-BioNTech, Oxford-AstraZeneca and Moderna vaccines.

Conclusion: In fully vaccinated individuals, symptomatic infection with the delta variant was significantly reduced, and therefore, vaccinations play an important role to assist the fight against delta variant.

Keywords: COVID-19; Delta variant; SARS-CoV-2; Variants.

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Conflict of interest statement

All authors have no conflict of interest to declare.

Figures

Fig. 1
Fig. 1
Flow diagram of studies included in the systematic review and meta-analysis
Fig. 2
Fig. 2
Pooled estimate for the prevalence of SARS-CoV-2 symptomatic infection with Delta variant [B.1.617.2] after the first dose of COVID-19 immunization stratified by the vaccine type
Fig. 3
Fig. 3
Pooled estimate for the prevalence of SARS-CoV-2 symptomatic infection with Delta variant [B.1.617.2] after the second dose of COVID-19 immunization stratified by the vaccine type
See this image and copyright information in PMC

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Supplementary concepts