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COVID-19 vaccines effectiveness against SARS-CO-V-2 infection among persons attending RT-PCR centre at a medical College Hospital in Telangana: A case control study

Background: In January 2021, India drug regulator issued restricted emergency approval for COVAXIN and COVISHIELD which were manufactured in India. On mid-January 2021, in India, there were 10.5 million confirmed cases and 0.15 million deaths. Objectives: The objectives were to evaluate vaccine effectiveness (VE) of India made Covid-19 vaccines against SARS-CoV-2 infection. Methods: A test negative case control study was conducted from May 2021 to December 2021 for duration of 8 months among people attending an RT-PCR centre at a medical college Hospital for RT-PCR test. The baseline characteristics and RT-PCR report and preliminary data about vaccine status were collected from the RT-PCR centre. The exposure to vaccination was enquired via Phone call or was checked with data available with the health authorities. Results: After applying inclusion exclusion criteria, case and control definitions, a total of 380 participants (95cases and 285 controls) were included. The adjusted VE of two doses of COVISHIED vaccine against symptomatic SARS-CoV-2 infection was 52.2% (95% CI, 41.7 to 62.1) and single dose was 40.88% (95% CI, 31.26 to 51.29). The adjusted VE of two doses of COVAXIN vaccine against SARS-CoV-2 infection was 39% (95% CI, 29.40 to 49.27). The overall VE was 48.20% (95% CI, 37.90 to 58.22) for two doses of any vaccines. Conclusions: India made vaccines were nearly 50% effective. Similar results show by different studies with a margin of 10-20% difference. Further new studies should be conducted as new variants of SARS-CoV-2 are emerging, and we do not know how the vaccine works against the variants and booster doses were required or not. Key words: Vaccine effectiveness, RT-PCR test, Covid-19 disease, COVAXIN, COVISHIELD, SARS-Co-V-2 infection