The falling rate of daily Covid-19 infections and massive vaccination drive- both have raised hopes that an eventual third wave may not be as devastating as the second one. But the mutant viruses lurking and a festive season ahead. Experts have expressed guarded optimism. But the question remains unanswered that 'When will be India have herd immunity?' AIIMS director Dr. Randeep Guleria speaks to Aaj Tak over the Covid-19 pandemic. Watch the video to know more.