The race for an indigenous vaccine against the novel coronavirus is on in earnest. Human trials using the vaccine candidates of two companies — Bharat Biotech and Zydus Cadila — are currently on in six cities in as many states. The latest subject was a 30-year-old man who on Friday was the first person from Delhi to be given a 0.5 ml intramuscular injection of Bharat Biotech (BB)’s Covaxin at AIIMS. The first phase will involve over 500 volunteers, all healthy and between the ages of 18 and 55 with no comorbidities. Phase I trials involve studying the safety of the vaccine in a healthy individual and will decide the right dosage that will be effective against the virus.