India has announced it will soon open its vaccination programme to every adult in response to soaring Covid-19 infections – a measure that could further strain supplies in parts of the world reliant on Indian-made vaccines for their own campaigns. From 1 May, Indian states will be free to administer doses to anyone aged older than 18, the central government announced on Monday as part of a package of policies to tackle a second wave that has overwhelmed hospitals and led to oxygen shortages across the country. Delhi’s government was one of several local administrations to announce new quarantine measures. The capital’s chief minister, Arvind Kejriwal, said Delhi was facing a “grim” situation and needed to lock down for at least six days from Monday evening. The daily death toll in India has climbed to more than 1,500, the highest figure since the beginning of the pandemic. Some public health specialists have blamed the surge in infections on a highly infectious “double mutant” variant spreading in cities and villages that had relaxed social distancing after six months of falling caseloads. India has tried to ramp up the speed of its national vaccination programme in response but is limited by how much its manufacturers can produce. Many vaccination centres have had to ration supplies even though the jab is currently only available to people older than 45. The government said last week it had a stock of fewer than 27m doses, enough to last about nine days at the current rate of vaccination. Reuters reported on Sunday that the government was likely to agree to give a $30m grant to the Serum Institute of India, the world’s largest vaccine manufacturer, to boost its monthly production capacity to 100m, up from the 50-60m doses it has been producing to date. Removing age restrictions opens up access to the vaccine to at least 400 million more people, which could mean the government allows Indian manufacturers to export fewer vaccines, including as part of the Covax initiative, a multilateral programme intended to help developing and middle-income countries. India has already vastly scaled down the amount of vaccines it is shipping abroad, exporting only about 2m doses in past weeks, compared with 64m between January and March. Shipments to developing countries through the Covax programme have continued but in lower numbers than was projected before the second wave. The Serum Institute has said its manufacturing capacity is being constrained by a US export ban on raw material products it needs to produce more doses. “Respected @POTUS, if we are to truly unite in beating this virus, on behalf of the vaccine industry outside the US, I humbly request you to lift the embargo of raw material exports out of the US so that vaccine production can ramp up,” Adar Poonawalla, the chief of the institute, tweeted on Friday. The White House has not responded. The British prime minister, Boris Johnson, on Monday cancelled an upcoming state visit to Delhi, citing the scale of the outbreak in a statement released with the Indian government.