Even as the Haryana Health Minister, a volunteer in the third phase of vaccine trials for India's first indigenous COVID-19 vaccine, said he has tested positive for the virus, medical experts in the national capital say that no vaccine makes a person 100 percent immune from any disease. Talking to ANI, experts explained that once an antigen enters the body, it all depends on the strength of the immune system to create the antibody against it.

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Doctor SP Byotra, Chairman Department of Medicine, Sir Ganga Ram Hospital said: "There is a notion in the public that once a person gets vaccinated he becomes immune to any infection but this is an antigen that will produce antibodies in a person within a stipulated time. If a person gets the infection even after getting the vaccine then it should not be considered as a failure of the vaccine." Several vaccines required to be given in two doses. First is a half dose which starts stimulating the production of antibodies followed by the second which maintains a high level of antibodies in the body.

Dr Prasun Chatterjee, Associate Professor, Department of Geriatric Medicine, All India Institute of Medical Sciences said: "Covaxin is a killed virus which once infused in a human body some of the property like surface glycoprotein stimulates antibodies. What is dangerous for COVID is the glycoprotein. One-shot gives partial protection but booster is better. It stimulates the immune system twice." Stressing on COVID- appropriate behaviour even after being immunised Chatterjee said that one has to follow all health protocols even when the person is immunised. Both the Serum Institute of India and Bharat Biotech vaccines are in their phase three trial.

The first phase trial includes very seriously ill patients where no risk is taken followed by phase two trial which was been conducted on a particular group of patients. Under these phases, it is being observed if the adequate antibody is produced or not. In last phase trial which is presently going on in the world, a lot more people are vaccinated under various age groups including children, which will determine if the vaccine was ready to be in the market or not.

The Haryana's Health Minister, 67, who volunteered for Covaxin trial and was administered a dose on November 20 tweeted about being corona positive on December 5 morning. As per the procedure, a second dose was scheduled after 28 days. In a press release issued by Bharat Biotech stated: "COVAXIN™ clinical trials are based on two doses schedule, given 28 days apart. The vaccine efficacy will be determined 14 days post the second dose. COVAXIN™ has been designed to be efficacious when subjects receive both doses and post the 14 day period after the second dose." Covaxin's phase three trials are double-blinded and randomised, where 50 percent of subjects will receive the vaccine and 50 percent of subjects will receive a placebo.