On January 16, 2021, India launched its coronavirus disease 2019 (COVID-19) vaccination campaign with two vaccines: Oxford–AstraZeneca ChAdOx1 nCoV-19 (a chimp adenoviral vector vaccine manufactured by Serum Institute of India; Covishield) and BBV152 (a whole-virion inactivated vaccine manufactured by Bharat Biotech; Covaxin).
Study: Effectiveness of an inactivated virus-based SARS-CoV-2 vaccine, BBV152, in India: a test-negative, case-control study. Image Credit: Viacheslav Lopatin.
Initially, only health-care workers and front-line workers (such as police officers, paramilitary forces, sanitation workers, and disaster relief volunteers) were eligible for vaccination.
On March 1, 2021, eligibility was expanded to include Indian residents over the age of 60 or 45–60 years with comorbidities, and then to all residents over the age of 45 on April 1, 2021. In India, vaccination is currently being offered to all adults aged 18 and up as part of the national COVID-19 vaccination drive.
Safety and immunogenicity data from phase 1 and phase 2 trials were used to secure approval for BBV152. Following that, the phase 3 trial (NCT04641481) found that the vaccination was effective against symptomatic laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by 77.8 %. The efficacy against severe disease was 93.4%, asymptomatic infection was 63.6 %, and the efficacy against the delta (B.1.617.2) variant of concern was 65.2 %.
Because performance in a real-world situation typically differs from measured efficacy under controlled trial settings, assessing vaccine effectiveness after licensure is an important part of any vaccine roll-out. In a study published in The Lancet Infectious Diseases, researchers investigated the effectiveness of the BBV152 vaccine among employees of the All India Institute of Medical Sciences.
The study
A total of 3,732 persons were tested for SARS-CoV-2 at the institute's COVID-19 sample collecting site between April 15 and May 15, 2021.
After excluding people who were not institute employees (n=325), had invalid test reports (n=227), had received the ChAdOx1 nCoV-19 vaccine (n=52), had missing data on vaccination status and dates (n=178), and were asymptomatic at the time of testing (n=236), there were 2,714 symptomatic tested participants, 1,617 of whom tested positive for SARS-CoV-2 (cases) and 1,097 of whom tested negative.
Except for a higher proportion of those working in COVID-19 areas among cases than among controls, the characteristics of participants removed due to missing vaccination data were broadly similar across cases and controls.
The median time between receiving the last vaccine dose and the end of the study period (May 15, 2021) was 37 days for those who received one dose and 50 days for those who received two doses.
After controlling for age, gender, previous SARS-CoV-2 infection, calendar time, and the number of BBV152 doses received, cases had a higher likelihood of working in a COVID-19 area than controls, though this was not statistically significant.
With an interval of at least 14 days between administration of the second dose and day of testing, the unadjusted efficacy of two doses of BBV152 against symptomatic real-time polymerase chain reaction reverse transcription (RT-PCR)-confirmed SARS-CoV-2 was 53%. The effectiveness was assessed to be 50% after adjustments. Two doses given at least 28 days before testing was 46% effective, and two doses given at least 42 days before testing were 57% effective. After removing participants who had previously been infected with SARS-CoV-2, the adjusted efficacy of two doses given at least 14 days before testing was 47%.
The estimated effectiveness of two doses of BBV152 given at least 14 days before testing was numerically higher among participants tested in the third and second ten days of the 30-day study period than among those tested in the first ten days. The estimated adjusted effectiveness of a single dose of BBV152 administered at least seven days before testing was 1%, and 1% when administered at least 21 days before testing.
Implications
This study demonstrated the efficacy of two doses of BBV152 against symptomatic RT-PCR-confirmed SARS-CoV-2 cases during a surge in cases dominated by the delta variant. The effectiveness should be evaluated considering the surge conditions and the delta variant's potential for immune evasion.
The findings highlight the importance of rapid roll-out to ensure complete vaccination with two doses is completed on time while continuing to implement and adhere to non-pharmacological interventions, particularly during case surges.
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