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Systematic Review

Effectiveness of COVID-19 Vaccines against Delta (B.1.617.2) Variant: A Systematic Review and Meta-Analysis of Clinical Studies

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Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
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Renal Division, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
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John B. Little Center for Radiation Sciences, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA
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Department of Virology, Faculty of Medicine, Iran University of Medical Science, Tehran 1449614535, Iran
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Neuroscience Research Center, Guilan University of Medical Sciences, Rasht 4188794755, Iran
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Department of Family Medicine, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
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Deputy of Research and Technology, Ministry of Health and Medical Education, Tehran 1467664961, Iran
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Non-Communicable Diseases Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran University of Medical Sciences, Tehran 1411713139, Iran
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Hematology, Oncology and Stem Cell Transplantation Research Center, Research Institute for Oncology, Hematology and Cell Therapy, Tehran University of Medical Sciences, Tehran 1411713131, Iran
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Department of Mathematics, Yasouj University, Yasouj 7493475918, Iran
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Digestive Diseases Research Center, Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran 1411713135, Iran
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Inflammation Research Center, Tehran University of Medical Sciences, Tehran 1411713137, Iran
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Authors to whom correspondence should be addressed.
Academic Editors: Ger Rijkers and Jean-Luc Murk
Vaccines 2022, 10(1), 23; https://doi.org/10.3390/vaccines10010023
Received: 15 November 2021 / Revised: 19 December 2021 / Accepted: 21 December 2021 / Published: 25 December 2021
(This article belongs to the Topic Global Analysis of SARS-CoV-2 Serology)
The high transmissibility, mortality, and morbidity rate of the SARS-CoV-2 Delta (B.1.617.2) variant have raised concerns regarding vaccine effectiveness (VE). To address this issue, all publications relevant to the effectiveness of vaccines against the Delta variant were searched in the Web of Science, Scopus, EMBASE, and Medline (via PubMed) databases up to 15 October 2021. A total of 15 studies (36 datasets) were included in the meta-analysis. After the first dose, the VE against the Delta variant for each vaccine was 0.567 (95% CI 0.520–0.613) for Pfizer-BioNTech, 0.72 (95% CI 0.589–0.822) for Moderna, 0.44 (95% CI 0.301–0.588) for AstraZeneca, and 0.138 (95% CI 0.076–0.237) for CoronaVac. Meta-analysis of 2,375,957 vaccinated cases showed that the Pfizer-BioNTech vaccine had the highest VE against the infection after the second dose, at 0.837 (95% CI 0.672–0.928), and third dose, at 0.972 (95% CI 0.96–0.978), as well as the highest VE for the prevention of severe infection or death, at 0.985 (95% CI 0.95–0.99), amongst all COVID-19 vaccines. The short-term effectiveness of vaccines, especially mRNA-based vaccines, for the prevention of the Delta variant infection, hospitalization, severe infection, and death is supported by this study. Limitations include a lack of long-term efficacy data, and under-reporting of COVID-19 infection cases in observational studies, which has the potential to falsely skew VE rates. Overall, this study supports the decisions by public health decision makers to promote the population vaccination rate to control the Delta variant infection and the emergence of further variants. View Full-Text
Keywords: COVID-19; SARS-CoV-2; SARS-CoV-2 variants; SARS-CoV-2 B.1.617.2 variant vaccines; Delta variant; efficacy; side effect; meta-analysis; effectiveness COVID-19; SARS-CoV-2; SARS-CoV-2 variants; SARS-CoV-2 B.1.617.2 variant vaccines; Delta variant; efficacy; side effect; meta-analysis; effectiveness
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MDPI and ACS Style

Pormohammad, A.; Zarei, M.; Ghorbani, S.; Mohammadi, M.; Aghayari Sheikh Neshin, S.; Khatami, A.; Turner, D.L.; Djalalinia, S.; Mousavi, S.A.; Mardani-Fard, H.A.; Kasaeian, A.; Turner, R.J. Effectiveness of COVID-19 Vaccines against Delta (B.1.617.2) Variant: A Systematic Review and Meta-Analysis of Clinical Studies. Vaccines 2022, 10, 23. https://doi.org/10.3390/vaccines10010023

AMA Style

Pormohammad A, Zarei M, Ghorbani S, Mohammadi M, Aghayari Sheikh Neshin S, Khatami A, Turner DL, Djalalinia S, Mousavi SA, Mardani-Fard HA, Kasaeian A, Turner RJ. Effectiveness of COVID-19 Vaccines against Delta (B.1.617.2) Variant: A Systematic Review and Meta-Analysis of Clinical Studies. Vaccines. 2022; 10(1):23. https://doi.org/10.3390/vaccines10010023

Chicago/Turabian Style

Pormohammad, Ali, Mohammad Zarei, Saied Ghorbani, Mehdi Mohammadi, Saeideh Aghayari Sheikh Neshin, Alireza Khatami, Diana L. Turner, Shirin Djalalinia, Seied A. Mousavi, Heydar A. Mardani-Fard, Amir Kasaeian, and Raymond J. Turner. 2022. "Effectiveness of COVID-19 Vaccines against Delta (B.1.617.2) Variant: A Systematic Review and Meta-Analysis of Clinical Studies" Vaccines 10, no. 1: 23. https://doi.org/10.3390/vaccines10010023

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