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. 2021 Oct 11:149:e224.
doi: 10.1017/S0950268821002247.

Effectiveness of COVID-19 vaccine in preventing infection and disease severity: a case-control study from an Eastern State of India

Chandramani Singh  1 , Bijaya Nanda Naik  1 , Sanjay Pandey  1 , Bijit Biswas  1 , Binod Kumar Pati  2 , Manisha Verma  1 , Prabhat Kumar Singh  3
Affiliations

Effectiveness of COVID-19 vaccine in preventing infection and disease severity: a case-control study from an Eastern State of India

Chandramani Singh et al. Epidemiol Infect. .

Abstract

Effectiveness of corona virus disease-19 (COVID-19) vaccines used in India is unexplored and need to be substantiated. The present case-control study was planned to elicit the effectiveness of COVID-19 vaccines in preventing infection and disease severity in the general population of Bihar, India. This case-control study was conducted among people aged ≥45 years during April to June 2021. The cases were the COVID-19 patients admitted or visited All India Institute of Medical Sciences (AIIMS), Patna, Bihar, India, and were contacted directly. The controls were the individuals tested negative for severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) at the Virology laboratory, AIIMS-Patna and contacted telephonically for collection of relevant information. The vaccine effectiveness (VE) was calculated by using the formula (VE = 1 - odds ratio). The adjusted VE for partial and full vaccination were estimated to be 52.0% (95% confidence interval (CI) 39.0-63.0%) and 83.0% (95% CI 73.0-89.0%) respectively for preventing SARS CoV-2 infection. The sub-group analyses of the cases have shown that the length of hospital stays (LOS) (partially vaccinated: 9 days vs. unvaccinated: 12 days; P = 0.028) and the severity of the disease (fully vaccinated: 30.3% vs. partially vaccinated: 51.3% and unvaccinated: 54.1%; P = 0.035) were significantly low among vaccinated compared to unvaccinated individuals. To conclude, four out of every five fully vaccinated individuals are estimated to be protected from contracting SARS CoV-2 infection. Vaccination lowered LOS and chances of development of severe disease.

Keywords: COVID-19; Case-control studies; India; SARS-CoV-2; effectiveness; vaccines.

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Conflict of interest statement

None.

Figures

Fig. 1.
Fig. 1.
Flowchart showing recruitment of the cases and controls. COVID-19, corona virus disease-19; RT-PCR, reverse transcriptase polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus-2; RNA, ribonucleic acid; H/O, history of; ILI: influenza-like illness.
Fig. 2.
Fig. 2.
Bar chart showing predominant reasons for not receiving COVID-19 vaccination. COVID-19, corona virus disease-19.
See this image and copyright information in PMC

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