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.

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.

Role of sociometry in determining the spread of Covid-19 cases amidst lockdown strategies

India implemented nationwide lockdown to control COVID-19 pandemic since March 2020. Despite lockdown for 100 days, the incidence of covid-19 does not seem to abate. Lockdown induced productivity loss caused severe economic stress. In any pandemic, initial lockdown is necessary for every country to ensure preparedness and public awareness. India erred in prolonging the initial spell of lockdown. During lockdown infected person will spend more time with family members and neighbours thereby infecting all with increase in k-value. In the absence of lockdown they may not find so much spare time to spend with his/her family or to visit neighbours with decrease in k-value. Although lockdown in India has reduced the rapidity of spread by bringing down R0to 1.27, it was achieved at the cost of prolonging the duration of the epidemic. In the absence of adequate herd immunity, lockdown may flatten the curve but area under the curve (AUC) will remain unaltered. The idea of lifting the lockdown with an aim of developing herd immunity in 60% of the younger population appears to be promising. Reverse quarantine of high-risk population appears to be a cost-effective method of containing the COVID pandemic in resource restricted countries like India.