Interim results from a phase 3 clinical trial of the BBV152 Bharat Biotech COVID-19 vaccine from India show that two doses offer 77.8% efficacy against symptomatic infection, according to a study today in The Lancet.
Just last week the World Health Organization (WHO) approved emergency use of the vero cell–derived vaccine in adults. It is the eighth COVID-19 vaccine to receive WHO emergency use listing.
Led by Bharat researchers, the study involved 24,419 participants aged 18 to 97 years at 25 hospitals in India 2 weeks after the second dose of the vaccine from Nov 16, 2020, to May 17, 2021. At the time, India experienced a peak of more than 400,000 new daily COVID-19 cases, including those caused by the Delta (B1617.2) variant.
Participants were randomly assigned to receive either two doses 28 days apart (12,221 participants) or a placebo (12,198). Of all participants, 2,750 (11.3%) were older than 60 years, and 5,724 of all ages (23.4%) reported having one or more chronic medical conditions, such as cardiovascular disease, diabetes, and obesity.
Lower efficacy against Delta
Twenty-four of 8,471 fully vaccinated participants (0.28%) tested positive for COVID-19, compared with 106 of 8,502 (1.2%) of the unvaccinated group, for an estimated vaccine effectiveness of 77.8%.
Among 16,973 symptomatic participants who initially tested negative for antibodies to SARS-CoV-2, 130 (0.77%) tested positive for COVID-19. Sixteen cases of severe systemic illness; respiratory failure; shock; significant acute kidney, liver, or neurologic dysfunction; admission to an intensive care unit (ICU); or death occurred, 1 among the vaccinated and 15 among the placebo group.
The researchers, however, caution that because the data are preliminary, more studies with larger sample sizes must be conducted to determine vaccine effectiveness against severe illness and hospitalization.
The Bharat vaccine produced a strong neutralizing antibody response, as indicated by levels of antibodies 1 month after receipt of the second dose, across all age-groups. Vaccine-induced antibodies didn't show significantly lower neutralizing activity against the Alpha (B117) SARS-CoV-2 variant but did reduced activity against other variants of concern, including Delta and Gamma (P.1).
A preliminary analysis of efficacy against Delta found the vaccine to be 65% effective against symptomatic COVID-19 caused by the variant, but the researchers said the data are preliminary and need confirmation via future research.
Twelve percent of all participants reported an adverse event, with no differences between the groups. Most adverse events, the most common of which were headache, fatigue, and pain at the injection site, were mild and occurred within a week after vaccination. There were no reports of severe vaccine-related adverse events, serious allergic reactions, or death.
Vaccine may help address shortages in some nations
The study authors said that more research is needed to determine the vaccine's long-term safety profile and effectiveness against severe illness, hospitalization, and death, including infections caused by variants. Safety monitoring will continue for 1 year after administration of the first vaccine dose, they said.
Of note, the trial didn't include pregnant women, those living with HIV, or those with severe underlying medical conditions. After the WHO emergency use approval, the study's data and safety monitoring board and sponsor unmasked eligible placebo group participants so they could receive an approved COVID-19 vaccine, the authors said.
"The established efficacy of BBV152 against symptomatic infection could be crucial in further mitigating the COVID-19 pandemic," the researchers wrote. "The asymptomatic efficacy highlighted in our study had wide confidence intervals, necessitating further data. However, the result still has public health significance in terms of reducing transmission."
In a related commentary, Jing-Xin Li, PhD, and Feng-Cai Zhu, MSc, both of Jiangsu Provincial Center for Disease Control and Prevention in China, pointed out that the Bharat vaccine has received emergency use authorization in India, Iran, Mexico, and the Philippines, all countries that are experiencing high rates of COVID-19 and have low to moderate vaccine coverage. The vaccine, they added, can be stored at normal freezer temperatures.
"The roll-out of BBV152 might ease the ultra-cold chain requirements of other SARS-CoV-2 vaccine platforms, increase the finite global manufacturing capacity, and improve insufficient supply of vaccines which disproportionately affects low-income and middle-income countries," they wrote.
