Researchers say the India-made Covaxin vaccine is safe and produces a strong antibody response against coronavirus.
A peer-reviewed study, published in the Lancet on Wednesday, showed the drug has an efficacy of 77.8 per cent against symptomatic Covid-19 infection.
The vaccine also conferred 65.2 per cent protection against symptomatic infection from the more aggressive Delta variant, scientists found.
The study analysed data from a Phase 3 trial conducted in Indian hospitals between November 2020 and May 2021.
Researchers examined more than 25,000 participants aged 18 to 97. Of these, 2,433 were over 60 and 4,500 had pre-existing medical conditions.
Respondents reported only mild reactions to the vaccine, including headache, fatigue, and injection site pain, with no severe adverse events recorded.
Also known as BBV152, the vaccine is developed by Bharat Biotech in India and formulated from an inactivated Sars-CoV-2 antigen. Covaxin is administered in two separate doses, recommended to be taken 28 days apart.
The authors of the study say further research is needed to determine the vaccine’s long-term safety and effectiveness.
Bharat Biotech says it has stockpiled 20 million doses of Covaxin for India, with plans to manufacture 700 million doses by the end of 2021. The drug was given the green light by Indian regulators earlier this year after results of the Phase 2 trials.
In November, Covaxin was granted emergency use listing listing by the World Health Organisation, allowing the drug to be distributed under the Covax vaccine-sharing facility for lower to middle income countries.
Unlike mRNA vaccines, such as those developed by Pfizer-BioNTech and Moderna, Covaxin does not require sub-zero-degree storage and can instead be kept between 2ºC and 8ºC.
This makes it well suited to many poorer countries that have warm climates and often experience power cuts, particularly in more remote areas.
Earlier this month, the UK said it would recognise Covaxin as an approved vaccine for inbound travellers, alongside China's Sinovac and Sinopharm.