Effectiveness of the ChAdOx1 nCoV-19 Vaccine against Laboratory-confirmed Cases of COVID-19: A Test-negative Case-control Study from Central Kerala, India
Introduction: The COVID-19 pandemic continues to impact livelihoods worldwide, and in the absence of specific antivirals, the vaccine remains the main weapon against it. Assessing the effectiveness of vaccines against Coronovirus Disease 2019 (COVID-19) in practice is crucial as COVID-19 variant...
Main Authors: | , , , , , , |
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Format: | Article |
Language: | English |
Published: |
JCDR Research and Publications Private Limited
2023-10-01
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Series: | Journal of Clinical and Diagnostic Research |
Subjects: | |
Online Access: | https://www.jcdr.net/articles/PDF/18597/62932_CE[Ra1]_F[SK]_QC(SHK_SS)_PF1(VD_KM_OM)_PFA(KM_OM)_PB(VD_OM)_PN(KM).pdf |
Summary: | Introduction: The COVID-19 pandemic continues to impact
livelihoods worldwide, and in the absence of specific antivirals,
the vaccine remains the main weapon against it. Assessing the
effectiveness of vaccines against Coronovirus Disease 2019
(COVID-19) in practice is crucial as COVID-19 variants continue
to emerge, and public health decisions must be supported by
scientific risk-benefit considerations.
Aim: To determine the Vaccine Effectiveness (VE) of two doses
of the ChAdOx1 nCoV-19 (Covishield) vaccine in preventing
laboratory-confirmed COVID-19.
Materials and Methods: A test negative case control design was
used to determine the VE in total of 702 individuals which included
351 laboratory confirmed cases using Reverse Transcriptase
Polymerase Chain Reaction (RT-PCR) and 351 controls who
tested negative among those who attended the testing sites
of the Urban Family Health Centre of Government Medical
College Kottayam, Kerala, India from July 2021 to September
2021. Details regarding vaccination status, sociodemographic
factors, symptoms, and co-morbidities were collected from
consented and eligible participants. The collected information
was entered into a proforma, which was later entered into MS
Excel and analysed using R software version 4.1.3. The groups
were compared using binary logistic regression to calculate
the adjusted Odds Ratio (aOR) with adjustment for gender, age
group, education, occupation, presence of symptoms, and comorbidity status. VE% was calculated as 100 * (1-aOR).
Results: The median age (interquartile range) of cases and
control was 44 (33-57) years and 50 (35-60) years, respectively.
The VE of two doses of the ChAdOx1 nCoV-19 vaccine in
protecting against laboratory-confirmed COVID-19 was 87%
(95% CI 78-92), with an aOR of 0.13. A separate analysis
was conducted to determine the VE among symptomatic
individuals, which showed a VE of 89% (95% CI 79-94), with
an aOR of 0.11.
Conclusion: Two doses of the ChAdOx1 nCoV-19 vaccine are
protective against laboratory-confirmed cases of COVID-19. |
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ISSN: | 2249-782X 0973-709X |