First Real-World Study Reports Effectiveness of BBV152, a COVID-19 Vaccine Developed in India

The first real-world evaluation of BBV152, an Indian-developed COVID-19 vaccine, indicates that two vaccine doses result in 50% efficacy against symptomatic COVID-19.

Between April 15 and May 15, 2021, the study assessed 2,714 hospital workers at the All India Institute of Medical Sciences (AIIMS) in Delhi, India, who were symptomatic and underwent RT-PCR testing for COVID-19. During the study period, the delta variant was the predominant strain in India, accounting for approximately 80% of all confirmed COVID-19 cases.

BBV152 is a Vero cell-derived, inactivated whole-virion vaccine developed by Bharat Biotech (India). It is formulated with a novel adjuvant and administered in a two-dose regimen 28 days apart.

BBV152 was approved for emergency use in India in January 2021 for people aged 18 years. In November 2021, the World Health Organization (WHO) added BBV152 to its list of approved COVID-19 vaccines for emergency use.

This new study was conducted during India's second COVID-19 outbreak in a high-exposure population (healthcare workers) who were primarily offered the BBV152 vaccine, providing an unprecedented opportunity to evaluate its efficacy in the real world.

"Our study provides a more complete picture of how BBV152 performs in the field and should be considered in light of the COVID-19 surge in India, as well as the delta variant's possible immune evasive potential. Our findings add to the growing body of evidence that rapid vaccine rollout programs remain the most promising path forward for pandemic control, while public health policies must continue to incorporate additional protective measures such as mask use and social isolation," says Dr. Manish Soneja, Additional Professor of Medicine at AIIMS in New Delhi.

The study was conducted at AIIMS, a tertiary care and COVID-19 treatment center in New Delhi. The hospital's COVID-19 vaccination center is exclusively for COVID-19 vaccinations.

BBV152 will be available to all of its 23,000 employees beginning January 16, 2021. Between April 15 and May 15, 2021, researchers conducted a test-negative control study to determine the efficacy of the BBV152 vaccine against symptomatic RT-PCR confirmed SARS-CoV-2 infection.

1,617 employees tested positive for SARS-CoV-2 infection, while 1,097 tested negative. Positive cases were matched 1:1 in age and gender to negative RT-PCR tests (controls). Between cases and controls, the odds of receiving BBV152 vaccination were compared and adjusted for occupational exposure to COVID-19, previous SARS-CoV-2 infection, and infection dates.

After two doses of BBV152, with the second dose administered 14 or more days before undergoing RT-PCR testing, the adjusted vaccine effectiveness against symptomatic COVID-19 was 50%. Over a seven-week follow-up period, the effectiveness of two vaccine doses remained stable.

The majority of eligible participants were tested for SARS-CoV-2 infection during the first 20 days of the 30-day study, which coincided with the peak of the COVID-19 test positivity rate in India. Requests for testing gradually decreased toward the study's conclusion (from May 6 to May 15). The median interval between the last vaccine dose and the end of the study period (May 15, 2021) was 37 days (range, 7–119) days for those who received one dose and 50 days (range, 5–103) days for those who received two doses. The adjusted vaccine effectiveness of the first dose was low at 7 and 21 days, which is consistent with the performance of other vaccines against the delta variant and emphasizes the critical role of a second dose in achieving vaccine effectiveness.

"The study's findings corroborate previous research that two doses of BBV152 are required for maximum protection and that all vaccine roll-out plans must adhere to the recommended dosing schedule. Additional research is needed to determine how these findings translate to BBV152's efficacy against delta and other concerning COVID-19 variants, particularly those associated with severe infection, hospitalization, and death," says Dr. Parul Kodan, Assistant Professor of Medicine at AIIMS in New Delhi.

A critical component of any vaccine roll-out strategy is assessing the vaccine's effectiveness post-licensure in a real-world setting, as real-world performance frequently differs from that observed in controlled trials. Indeed, the authors acknowledge that the vaccine's estimated effectiveness is lower than that reported in a recently published phase 3 randomized control study of BBV152.

The authors note that several factors could account for the study's lower vaccine effectiveness. To begin, this study population included only hospital employees, who may be at a higher risk of infection with COVID-19 than the general population. Second, the study was conducted during the peak of India's second COVID-19 wave, which was characterized by high test positivity rates among hospital employees and Delhi residents. Thirdly, the prevalence of potentially harmful circulating variants, particularly delta, may have contributed to BBV152's reduced effectiveness.

The authors of the study acknowledge several limitations. Most importantly, this study does not provide an estimate of the vaccine's effectiveness against hospitalization, severe disease, or death, all of which require additional evaluation. Additionally, the study was not designed to determine vaccine effectiveness at various time points following vaccination or to determine whether vaccine effectiveness changed over time. Another limitation was the lack of data on comorbidities and prior COVID-19 infection, which may influence both health seeking behavior and vaccine efficacy. While the study was conducted during the delta variant's surge, patients with positive RT-PCR results were not tested for SARS-CoV-2 variants. As a result, the authors were unable to determine the vaccine's efficacy against symptomatic COVID-19 due to a specific variant. Further research should be conducted to determine the delta variant's vaccine escape potential.

"Our study took place at a time when the COVID-19 test positivity rate in Delhi was around 35% – the highest level since the pandemic began. It is critical to consider this when interpreting the effect of any vaccine. The availability of a safe and effective vaccine, as well as addressing vaccine hesitancy, are critical components of a successful universal vaccination program." Professor Naveet Wig, Head of Medicine at the AIIMS in New Delhi, concurred.

Dr. Ramachandran Thiruvengadam, Dr. Akshay Binayke, and Dr. Amit Awasthi of the Translational Health Science and Technology Institute (India), who were not involved in the study, write in a linked Comment, "The decline in vaccine effectiveness against SARS-CoV-2 infection during a delta-driven case surge is neither surprising nor exclusive to inactivated SARS-CoV-2 vaccines, including BBV152." The delta variant is extremely transmissible, infectious, and virulent, resulting in severe disease. These characteristics may have contributed to the vaccine's reduced effectiveness against symptomatic infections, which has been reported to be as low as 56% in multiple studies conducted worldwide... Future studies should place a premium on evaluating protection against moderate-to-severe COVID-19 infection... Faced with the challenge of protecting the largest possible proportion of the population, the ongoing vaccination campaign against SARS-CoV-2 should be maintained as a public health intervention, alongside strict adherence to other non-pharmacological interventions, particularly in the context of variant-driven surges."

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