Results of a test-negative, case-control study found that the inactivated whole-virion 2-dose BBV152 vaccine was effective against symptomatic SARS-CoV-2 infection during a surge of the Delta variant in a healthcare setting. These findings were published in The Lancet Infectious Diseases.

Researchers conducted a study among employees at a tertiary care hospital in India who had access to the 2-dose BBV152 vaccine from January 2021. Participants who had symptoms suggestive of SARS-CoV-2 infection during the peak of the second COVID-19 wave (April-May 2021) were evaluated for SARS-CoV-2 via reverse transcription polymerase chain reaction (RT-PCR) testing. Patients who tested positive for SARS-CoV-2 infection (cases) were matched in a 1:1 fashion on the basis of age and sex against those who tested negative (controls). The primary outcome was the effectiveness of the 2-dose BBV152 vaccine in decreasing the odds for symptomatic RT-PCR-confirmed SARS-CoV-2 infection, with the second vaccine dose administered at least 14 days prior to testing.

Among a total of 1068 participants included in the study, 54.5% were men, 44.3% were aged younger than 30 years, 33.8% were aged 31 to 40 years, 15.1% were aged 41 to 50 years, 6.4% were aged 51 to 60 years, and 0.5% were younger than 60 years. Of note, participants in control group were more likely to report a previous SARS-CoV-2 infection vs those in the cases group (11.1% vs 3.6%).

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Among participants in both the positive and negative SARS-CoV-2 groups, 555 and 447 were unvaccinated, 233 and 351 had received 1 vaccine dose, and 280 and 270 were fully vaccinated, respectively.

The researchers found that the adjusted effectiveness of the 2-dose BBV152 vaccine 14 days after administration of the second dose was 50% (95% CI, 33-62). However, the adjusted effectiveness of the vaccine was 46% (95% CI, 22-62) among participants who received the second vaccine dose 28 days prior to enrollment and 57% (95% CI, 21-76) among those who received the second vaccine dose 42 days prior to enrollment.

After the exclusion of participants with prior SARS-CoV-2 infection, the researchers found that the adjusted effectiveness of the BBV152 vaccine administered 14 days prior to enrollment was 47% (95% CI, 29-61). Of note, the adjusted effectiveness of the vaccine was increased among participants who were women (66%; 95% CI, 43-80) compared with men (38%; 95% CI, 12-57).

On analysis of all participants included in the unmatched cohort, the researchers noted that the adjusted effectiveness of the BBV152 vaccine was 44% (95% CI, 32-55).

This study was limited by the lack of available data on the duration of participants’ symptoms at enrollment as those who were tested for SARS-CoV-2 infection late into their disease course may have received a false-negative result due to decreased sensitivity of the RT-PCR. In addition, the study was underpowered to estimate changes in the effectiveness of the vaccine for different time intervals of vaccination, and there was a lack of available data on participants’ comorbidities.

The researchers concluded that “the effectiveness [of the BBV152 vaccine] should be analyzed in the context of surge conditions and the possible immune evasive potential of the Delta variant.”


Desai D, Khan AR, Soneja M, et al. Effectiveness of an inactivated virus-based SARS-CoV-2 vaccine, BBV152, in India: a test-negative, case-control study. Lancet Infect Dis. 2021;S1473-3099(21)00674-5. doi:10.1016/S1473-3099(21)00674-5