India launched its coronavirus disease 2019 (COVID-19) vaccination campaign on January 16, 2021, with two vaccines: Oxford–AstraZeneca ChAdOx1 nCoV-19 (a chimp adenoviral vector vaccine manufactured by Serum Institute of India; Covishield) and BBV152 (a chimp adenoviral vector vaccine manufactured by Serum Institute of India) (a whole-virion inactivated vaccine manufactured by Bharat Biotech; Covaxin).
Only health-care personnel and front-line workers (such as police, paramilitary forces, sanitation workers, and disaster relief volunteers) were initially eligible for vaccination.
Eligibility was expanded on March 1, 2021, to include Indian residents over the age of 60 or 45–60 years with comorbidities, and then on April 1, 2021, to all inhabitants over the age of 45. As part of the nationwide COVID-19 immunization drive in India, all adults aged 18 and up are being offered vaccination.
BBV152 was approved based on safety and immunogenicity data from phase 1 and phase 2 trials. The immunization was then demonstrated to be efficacious against symptomatic laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by 77.8% in a phase 3 trial (NCT04641481). The efficacy against severe disease was 93.4 percent, asymptomatic infection was 63.6 percent, and the delta (B.1.617.2) variation of concern had an efficacy of 65.2 percent.
Because vaccination effectiveness in the real world differs from that assessed in controlled trials, measuring vaccine effectiveness after licensure is an important aspect of every vaccine roll-out. Researchers looked into the effectiveness of the BBV152 vaccine among personnel of the All India Institute of Medical Sciences in a study published in The Lancet Infectious Diseases.
The research
Between April 15 and May 15, 2021, 3,732 people were tested for SARS-CoV-2 at the institute’s COVID-19 sample collection location.
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 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).
The characteristics of participants eliminated owing to missing vaccination data were largely similar between cases and controls, with the exception of a higher proportion of those working in COVID-19 areas among cases than among controls.
For those who received one dosage, the median time between getting the last vaccine dose and the conclusion of the study period (May 15, 2021) was 37 days, and for those who received two doses, it was 50 days.
Cases had a higher likelihood of working in a COVID-19 area than controls after controlling for age, gender, previous SARS-CoV-2 infection, calendar time, and the number of BBV152 doses received, albeit this was not statistically significant.
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% with a 14-day interval between administration of the second dosage and day of testing. After revisions, the effectiveness was estimated to be 50%. Two doses given at least 28 days before testing were successful in 46 percent of cases, and two doses given at least 42 days before testing were effective in 57 percent of cases. The adjusted efficacy of two doses given at least 14 days before testing was 47 percent after eliminating participants who had previously been infected with SARS-CoV-2.
Participants assessed in the third and second ten days of the 30-day research period had a numerically higher estimated effectiveness of two doses of BBV152 administered at least 14 days before testing than those evaluated in the first ten days. A single dose of BBV152 given at least seven days before testing had an estimated adjusted efficacy of 1%, while a dose given at least 21 days before testing had an estimated adjusted effectiveness of 1%.
Implications
During a surge in cases mainly by the delta form, this study revealed the effectiveness of two doses of BBV152 against symptomatic RT-PCR-confirmed SARS-CoV-2 infections. The effectiveness should be assessed in light of the surge conditions and the delta variant’s immune evasion capabilities.
The findings emphasize the necessity of a rapid roll-out to guarantee that complete immunization with two doses is finished on time, while continuing to adopt and adhere to non-pharmacological therapies, especially during case surges.
Journal reference:
- Desai, D. et al. (2021) “Effectiveness of an inactivated virus-based SARS-CoV-2 vaccine, BBV152, in India: a test-negative, case-control study”, The Lancet Infectious Diseases.
