Bharat Biotech International Limited has announced that its Covid-19 vaccine candidate, COVAXIN, has shown positive efficacy in animal studies and generated robust immune responses.COVAXIN, developed by the Indian Council of Medical Research and Bharat Biotech, is being tested at 12 institutes across India. This indigenous vaccine is one of the front runners in the race for a coronavirus vaccine in the country."Bharat Biotech proudly announces the animal study results of COVAXIN -- these results demonstrate the protective efficacy in a live viral challenge model," the Hyderabad-based firm said.The drug-maker added: "The vaccine candidate was found to generate robust immune responses. Thus, preventing infection and disease in the primates upon high amounts of exposure to live SARS-CoV-2 virus."During the procedure, a two-dose vaccination regimen of inactivated SARS-CoV-2 vaccine candidates was administered in 20 rhesus macaques, divided into four groups.One group was administered with placebo, while three groups were immunised with three different vaccine candidates at zero and 14 days. All the macaques were exposed to viral challenge 14 days after the second dose."The results showed protective efficacy, increasing SARS-CoV-2 specific IgG and neutralizing antibodies, reducing replication of the virus in the nasal cavity, throat, and lung tissues of the monkeys," Bharat Biotech added.No evidence of pneumonia was observed by histopathological examination in vaccinated groups, unlike the placebo group. Adverse events were not seen in animals immunised with a two-dose vaccination regimen.