Background
On 16 Jan 2021, India launched its immunization program against COVID-19. Among the first recipients were 1.59 million Health Care Workers (HCWs) and Frontline Workers (FLWs) of the Indian Armed Forces, who were administered COVISHIELD (Astra Zeneca). We present an interim analysis of vaccine effectiveness (VE) estimates till 30 May 2021.
Methods
The VIN-WIN cohort study was carried out on anonymized data of HCWs and FLWs of Indian Armed Forces. The existing surveillance system, enhanced for COVID-19 monitoring, was sourced for data. The cohort transitioned from Unvaccinated (UV) to Partially Vaccinated (PV) to Fully Vaccinated (FV), serving as its own internal comparison. Outcomes studied in the three groups were breakthrough infections and COVID related deaths. Incidence Rate Ratio (IRR) was used to compare outcomes among the three groups to estimate VE.
Results
Data of 1,595,630 individuals (mean age 27.6 years; 99% male) over 135 days was analysed. Till 30 May 21, 95.4% and 82.2% were partially and fully vaccinated. The UV, PV and FV compartments comprised 106.6, 46.7 and 58.7 million person-days respectively. The number of breakthrough cases in the UV, PV and FV groups were 10061, 1159 and 2512; while the deaths were 37, 16 and 7 respectively. Corrected VE was 91.8–94.9% against infections.
Conclusion
Interim results of the VIN-WIN cohort study of 1.59 million HCWs and FLWs of Indian Armed Forces showed a ∼93% reduction in COVID-19 breakthrough infections with COVISHIELD vaccination.
The study highlights the importance of Streptococcus pneumoniae as a causative organism for outbreaks of community acquired pneumonia (CAP) in large residential training institutions and reiterates the need for formulating a policy for continuous surveillance. It also highlights the importance of the novel method of using chemoprophylaxis for control of an ongoing outbreak of CAP.
error taken at 5% and expected deviation as 1% for HBV and 0.5% for HCV, a minimum sample size of 1120 for HBV prevalence study and 1521 for HCV prevalence study was obtained. The sample was selected from the study population of army units located in the same station by the method of multistage random sampling.A detailed questionnaire was developed to study the risk factors for transmission of HBV and HCV infections and was administered to all serving personnel during sample collection.
RESULTSA total of 1511 samples were collected from serving soldiers and all of these, were tested for HBsAg and anti-HCV.HBV: Overall point prevalence of HBsAg positivity in serving soldiers was found to be 1.25% (95% CI = 0.69%-1.81%).HCV: Of the 1151 samples tested for anti-HCV, not even one tested positive.Questionnaire on likely risk factors of HBV infection were administered to 1511 serving soldiers; completed questionnaires were received from 1262 persons and these were used for analysis of results.Mean age of the responders was 31.3 years with SD of 5.3 (range 19-46 years). Around 97% responders were personnel below officer rank and 95.6% were educated more than primary level (Table 1).History of having taken injections from civil medical practitioners was observed to be a highly significant risk factor (P < 0.001) with OR = 10.22 (95% CI = 3.29-30.68), thus indicating that injections from civil increased the risk of infection by ten times (Table 2). Past history of surgery (OR = 5.24), undergoing dental procedure (OR = 3.17), habit of sharing razors (OR = 9.09) were observed to have increased risk of HBV infection with, however the risk was not statistically significant in the study group.
DISCUSSIONFindings of the study indicate that over all seroprevalence of HBV infection among population of Armed Forces was 1.25%. This is lower than 2.4% calculated as true prevalence in non-tribal
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