Effectiveness of BBV152/Covaxin and AZD1222/Covishield vaccines against severe COVID-19 and B.1.617.2/Delta variant in India, 2021: a multi-centric hospital-based case-control study

Abstract

Objectives: India introduced BBV152/Covaxin and AZD1222/Covishield vaccines in January 2021. We estimated the effectiveness of these vaccines against severe COVID-19 among individuals aged ≥45 years.

Methods: We did a multi-centric, hospital-based, case-control study between May and July 2021. Cases were severe COVID-19 patients, and controls were COVID-19 negative individuals from 11 hospitals. Vaccine effectiveness (VE) was estimated for complete (2 doses ≥ 14 days) and partial (1 dose ≥ 21 days) vaccination; interval between two vaccine doses and vaccination against the Delta variant. We used the random effects logistic regression model to calculate the adjusted odds ratios (aOR) with a 95% confidence interval (CI) after adjusting for relevant known confounders.

Results: We enrolled 1143 cases and 2541 control patients. The VE of complete vaccination was 85% (95% CI: 79-89%) with AZD1222/Covishield and 71% (95% CI: 57-81%) with BBV152/Covaxin. The VE was highest for 6-8 weeks between two doses of AZD1222/Covishield (94%, 95% CI: 86-97%) and BBV152/Covaxin (93%, 95% CI: 34-99%). The VE estimates were similar against the Delta strain and sub-lineages.

Conclusion: BBV152/Covaxin and AZD1222/Covishield were effective against severe COVID-19 among the Indian population during the period of dominance of the highly transmissible Delta variant in the second wave of the pandemic. An escalation of two-dose coverage with COVID-19 vaccines is critical to reduce severe COVID-19 and further mitigate the pandemic in the country.

Keywords: AZD1222/Covishield; BBV152/Covaxin; COVID-19 vaccines; Delta variant; Effectiveness; India.

Figure 1

Maximum likelihood tree of the 450 SARS-CoV-2 genomes in this study: A Maximumlikelihood tree of the 448 SARS-CoV-2 sequences retrieved in this study, along with the representative SARS-Cov-2 sequences (n = 12) from different clades. Tamura-Nei model with a bootstrap replication of 1000 cycles was used to assess statistical robustness. Four major sub-lineages of the Delta variant and other pangolin lineages observed in this study are marked on branches in different colors. Sub-lineage-I-IV is marked in red, dark green, violet and orange colors on the nodes. Kappa sequence is marked in brown color. The representative pangolin lineages are also marked on branches in different colors. FigTree v1.4.4 and Inkscape were used to visualize and edit the generated tree.