Tests on mixing vaccines and the effectiveness of a single dose of Covishield will begin soon in the government’s new strategy at a time the shortage of Covid shots has slowed down vaccinations. Sources say a study on mixing two different vaccines will start in a month and will likely be completed in two to two and a half months. Recently, after 20 people were accidentally injected with two different vaccines, the centre had ruled out any cause for concern. VK Paul, NITI Aayog member and the head of India’s Covid task force, had said in-depth research was needed to check whether mixing vaccines is effective. This is a key aspect of the new vaccination strategy devised in line with the target of one crore inoculations daily by mid-July.