NEW DELHI - As India moves to roll out one of the world's biggest vaccination drives, an app called CoWIN (Covid Vaccine Intelligence Work) will be the "backbone" of the exercise to vaccinate its vast population. The vaccination drive comes with a whole set of challenges, including the seamless movement of the vaccine from the source to the vaccination centres, storing it at the right temperature throughout and identifying beneficiaries in order of priority, all of which can be difficult even in countries with smaller populations. But India, not lacking in technological prowess, is banking on the app. In the financial capital of Mumbai, the authorities have registered 225,000 health workers and front-line staff, including police, on the CoWIN App.