Mathematical calculations indicate that Covaxin may provide immunity against Covid-19 for 9 to 12 months, and there may be a booster shot after this period elapses, Y.K. Gupta, the President of AIIMS Bhopal and Jammu, told IANS.Stressing on the safety and effectiveness of Covaxin, Gupta, former Dean (Academics), and ex-Head, Department of Pharmacology, AIIMS, New Delhi, said that no death has been reported so far due to Covaxin, nor has there been any case of major side-effects, adding that more clarity will emerge by March end when data from Phase 3 trials will be available to establish the efficacy of Covaxin.The approval for Covaxin, the homegrown vaccine developed by Bharat Biotech, had faced unrelenting criticism, especially when it was administered to scores of healthcare workers during Phase 1 of the vaccination drive. The critics have badgered Covaxin's approval in the absence of Phase 3 trial data.Speaking to IANS, Gupta said, "These are not scientifically correct claims. Covaxin was approved for emergency use and the data from Phase 1 and Phase 2 trials, and the ongoing Phase 3 trials, suggest that it is safe and effective, and by March-end tentatively, the data from Phase 3 trials will be available to establish its efficacy."When queried on the safety of Covaxin and people developing side-effects after its administration, Gupta said: "The vaccine is being given to lakhs of people, and there are hardly any serious side-effects. Rather there are only minor side-effects, whuihg indicate the effectiveness of the vaccine. No death has been caused by Covaxin so far."Commenting on India's vaccine technology in the backdrop the new mutant coronavirus strain reported in a few countries, Gupta said: "The Indian vaccine technology with minor tweaking has the potential to address these new strains."Addressing the attack on the efficacy of Covaxin by many scientists globally, Yadav said they have made irresponsible comments."It is better to take Covaxin than having irreversible damage to lungs due to Covid-19. By March end, we will have more real-life evidence and there will be more clarity. If Phase 3 trials give good results, it will be a matter of pride... No adverse event has been reported so far," said Gupta.He added that the regulator approves a drug if its efficacy is found to be over 50 per cent, which has been the case for Covaxin, and emphasised that different hypothesis and extrapolation suggest that it will be effective."There should not be any vaccine hesitancy," Gupta said.