Effectiveness of COVID-19 Vaccines against Delta Variant (B.1.617.2): A Meta-Analysis

Rashidul Alam Mahumud; Mohammad Afshar Ali; Satyajit Kundu; Md Ashfikur Rahman; Joseph Kihika Kamara; Andre M N Renzaho

doi:10.3390/vaccines10020277

Effectiveness of COVID-19 Vaccines against Delta Variant (B.1.617.2): A Meta-Analysis

Vaccines (Basel). 2022 Feb 11;10(2):277. doi: 10.3390/vaccines10020277.

Authors

Rashidul Alam Mahumud^{1

2

3}, Mohammad Afshar Ali^{2

4

5}, Satyajit Kundu^{6

7}, Md Ashfikur Rahman⁸, Joseph Kihika Kamara^{9

10}, Andre M N Renzaho^{11

12}

Affiliations

¹ NHMRC Clinical Trials Centre, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW 2006, Australia.
² School of Business and Centre for Health Research, University of Southern Queensland, Toowoomba, QLD 4350, Australia.
³ Health Research Group, Department of Statistics, University of Rajshahi, Rajshahi 6205, Bangladesh.
⁴ Allied Health and Human Performance Unit, University of South Australia, Adelaide, SA 5001, Australia.
⁵ Department of Economics, Jagannath University, Dhaka 1100, Bangladesh.
⁶ Faculty of Nutrition and Food Science, Patuakhali Science and Technology University, Patuakhali 8602, Bangladesh.
⁷ School of Public Health, Southeast University, Nanjing 210009, China.
⁸ Development Studies Discipline, Khulna University, Khulna 9208, Bangladesh.
⁹ World Vision East Africa Regional Office, Karen, Off Ngong Road, Karen Road, Nairobi 50816, Kenya.
¹⁰ Centre for Humanitarian Leadership, Deakin University, Melbourne, Burwood, VIC 3125, Australia.
¹¹ School of Medicine, Translational Health Research Institute, Western Sydney University, Campbelltown, NSW 2150, Australia.
¹² Maternal, Child and Adolescent Health Program, Burnet Institute, Melbourne, VIC 3004, Australia.

Abstract

Objectives: The highly transmissible COVID-19 Delta variant (DV) has contributed to a surge in cases and exacerbated the worldwide public health crisis. Several COVID-19 vaccines play a significant role in a high degree of protection against the DV. The primary purpose of this meta-analysis is to estimate the pooled effectiveness of the COVID-19 vaccines against the DV in terms of risk ratio (RR) among fully vaccinated, compared to unvaccinated populations. Methods: We carried out a systematic review, with meta-analysis of original studies focused on COVID-19 vaccines effectiveness against a DV clinical perspective among fully COVID-19 vaccinated populations, compared to placebo (unvaccinated populations), published between 1 May 2021 and 30 September 2021. Eleven studies containing the data of 17.2 million participants were identified and included in our study. Pooled estimates of COVID-19 vaccines effectiveness (i.e., risk ratio, RR) against the DV with 95% confidence intervals were assessed using random-effect models. Publication bias was assessed using Egger's regression test and funnel plot to investigate potential sources of heterogeneity and identify any differences in study design. Results: A total population of 17.2 million (17,200,341 people) were screened for the COVID-19 vaccines' effectiveness against the DV. We found that 61.13% of the study population were fully vaccinated with two doses of COVID-19 vaccines. The weighted pooled incidence of COVID-19 infection was more than double (20.07%) among the unvaccinated population, compared to the fully vaccinated population (8.16%). Overall, the effectiveness of the COVID-19 vaccine against the DV was 85% (RR = 0.15, 95% CI: 0.07-0.31). The effectiveness of COVID-19 vaccines varied slidably by study designs, 87% (RR = 0.13, 95% CI: 0.06-0.30) and 84% (RR = 0.16, 95% CI: 0.02, 1.64) for cohort and case-control studies, respectively. Conclusions: The effectiveness of COVID-19 vaccines were noted to offer higher protection against the DV among populations who received two vaccine doses compared with the unvaccinated population. This finding would help efforts to maximise vaccine coverage (i.e., at least 60% to 70% of the population), with two doses among vulnerable populations, in order to have herd immunity to break the chain of transmission and gain greater overall population protection more rapidly.

Keywords: B.1.617.2; COVID-19 vaccines; delta variant; herd immunity; meta-analysis; vaccines effectiveness.

Publication types

Review