ABSTRACT
Importance: A surge of COVID-19 occurred from March to June 2021, in New Delhi, India, linked to the B.1.617.2 (Delta) variant of SARS-CoV-2. COVID-19 vaccines were rolled out for health care workers (HCWs) starting in January 2021. Objective: To assess the incidence density of reinfection among a cohort of HCWs and estimate the effectiveness of the inactivated whole virion vaccine BBV152 against reinfection. Design, Setting, and Participants: This was a retrospective cohort study among HCWs working at a tertiary care center in New Delhi, India. Exposures: Vaccination with 0, 1, or 2 doses of BBV152. Main Outcomes and Measures: The HCWs were categorized as fully vaccinated (with 2 doses and ≥15 days after the second dose), partially vaccinated (with 1 dose or 2 doses with <15 days after the second dose), or unvaccinated. The incidence density of COVID-19 reinfection per 100 person-years was computed, and events from March 3, 2020, to June 18, 2021, were included for analysis. Unadjusted and adjusted hazard ratios (HRs) were estimated using a Cox proportional hazards model. Estimated vaccine effectiveness (1 - adjusted HR) was reported. Results: Among 15â¯244 HCWs who participated in the study, 4978 (32.7%) were diagnosed with COVID-19. The mean (SD) age was 36.6 (10.3) years, and 55.0% were male. The reinfection incidence density was 7.26 (95% CI: 6.09-8.66) per 100 person-years (124 HCWs [2.5%], total person follow-up period of 1696 person-years as time at risk). Fully vaccinated HCWs had lower risk of reinfection (HR, 0.14 [95% CI, 0.08-0.23]), symptomatic reinfection (HR, 0.13 [95% CI, 0.07-0.24]), and asymptomatic reinfection (HR, 0.16 [95% CI, 0.05-0.53]) compared with unvaccinated HCWs. Accordingly, among the 3 vaccine categories, reinfection was observed in 60 of 472 (12.7%) of unvaccinated (incidence density, 18.05 per 100 person-years; 95% CI, 14.02-23.25), 39 of 356 (11.0%) of partially vaccinated (incidence density 15.62 per 100 person-years; 95% CI, 11.42-21.38), and 17 of 1089 (1.6%) fully vaccinated (incidence density 2.18 per 100 person-years; 95% CI, 1.35-3.51) HCWs. The estimated effectiveness of BBV152 against reinfection was 86% (95% CI, 77%-92%); symptomatic reinfection, 87% (95% CI, 76%-93%); and asymptomatic reinfection, 84% (95% CI, 47%-95%) among fully vaccinated HCWs. Partial vaccination was not associated with reduced risk of reinfection. Conclusions and Relevance: These findings suggest that BBV152 was associated with protection against both symptomatic and asymptomatic reinfection in HCWs after a complete vaccination schedule, when the predominant circulating variant was B.1.617.2.
Subject(s)
COVID-19/epidemiology , Health Personnel , Reinfection , SARS-CoV-2 , Adult , COVID-19/etiology , COVID-19/prevention & control , COVID-19 Vaccines/administration & dosage , Cohort Studies , Female , Humans , Immunogenicity, Vaccine , India/epidemiology , Male , Middle Aged , Surveys and Questionnaires , Tertiary Care Centers , Vaccines, Inactivated/administration & dosage , Virion/immunology , Young AdultABSTRACT
BACKGROUND AND AIMS: There seems to be hesitation in the general population in accepting COVID 19 vaccine because of associated myths and/or misinformation. This study is dedicated to develop and validate a tool to interpret vaccine acceptance and/or hesitancy by assessing the knowledge, attitude, practices, and concerns regarding the COVID vaccine. MATERIAL AND METHODS: Mixed methods study design was used. In phase 1, the questionnaire was developed through literature review, focus group discussion, expert evaluation, and pre-testing. In phase 2, the validity of the questionnaire was obtained by conducting a cross-sectional survey on 201 participants. The construct validity was established via principal component analysis. Cronbach's alpha value was used to assess the reliability of the questionnaire. RESULTS: The 39-item questionnaire to assess the knowledge, attitude, practices, and concerns regarding the COVID-19 vaccine was developed. The Cronbach's alpha value of the questionnaire was 0.86 suggesting a good internal consistency. CONCLUSION: The developed tool is valid to assess the knowledge, attitude, practices and concerns regarding the COVID-19 vaccine acceptance and/or hesitancy. It has the potential utility for healthcare workers and government authorities to further build vaccine literacy.