SARS-CoV-2 Reinfection Rate and Estimated Effectiveness of the Inactivated Whole Virion Vaccine BBV152 Against Reinfection Among Health Care Workers in New Delhi, India
Authors: Sumit Malhotra, Kalaivani Mani, Rakesh Lodha, Sameer Bakhshi, Vijay Prakash Mathur, Pooja Gupta, Saurabh Kedia, Jeeva Sankar, Parmeshwar Kumar, Arvind Kumar, Vineet Ahuja, Subrata Sinha, Randeep Guleria, Aman Dua, Shafi Ahmad, Ramadass Sathiyamoorthy, Ajay Sharma, Tabbu Sakya, Vikas Gaur, Shilpi Chaudhary, Swetambri Sharma, Divya Madan, Anvita Gupta, Shubi Virmani, Arti Gupta, Nidhi Yadav, Surbhi Sachdeva, Shilpi Sharma, Sachin Singh, Abhimanyu Pandey, Mukesh Singh, Divashree Jhurani, Swarnabha Sarkar, Amol Kumar Lokade, Atif Mohammad, Sabitri Pandit, Ritu Dubey, Ajay Kumar Singh, Naveen Gohar, Divyansh Soni, Arunangshu Bhattacharyya, Sabin Rai, Snikitha Tummala, Ishan Gupta, Sakshi Shukla
Journal: JAMA Network Open (2022)

<h3>Importance</h3> 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. <h3>Objective</h3> 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. <h3>Design, Setting, and Participants</h3> This was a retrospective cohort study among HCWs working at a tertiary care center in New Delhi, India. <h3>Exposures</h3> Vaccination with 0, 1, or 2 doses of BBV152. <h3>Main Outcomes and Measures</h3> 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 &lt;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. <h3>Results</h3> Among 15 244 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. <h3>Conclusions and Relevance</h3> 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.