India says it is “calibrating” its vaccine exports in an attempt to balance surging domestic demand with international orders, raising doubts over the Serum Institute’s capacity to meet its global commitments. New Delhi has suspended exports, potentially for weeks, while it expands its vaccination campaign to Indians aged 45 and older on April 1 but insists it has not banned drug shipments.

Harsh Vardhan, India’s health minister, said on Friday that the government planned to widen vaccination eligibility even further in the “near future” as the country struggled to contain an accelerating second wave of infections. Narendra Modi’s government recently ordered loom doses of the Oxford/AstraZeneca vaccine from the Serum Institute of India, the world’s largest vaccine manufacturer and leading Covax supplier, taking all the doses the company will produce in the upcoming weeks.

The Serum Institute is producing more than 70m doses a month, or 2.4m a day, though it has plans to expand production to loom doses a month by May. But if India’s vaccine demand shoots up to 5m a day as targeted, it would struggle to meet its international orders.

“We had stated that keeping in view the domestic requirements of the phased rollout, India will continue to supply Covid-19 vaccines to partner countries over the coming weeks and months in a phased manner,” said a government official. “Given our current manufacturing capacity and requirements of national vaccination programmes, there may be a need to calibrate the supply schedules from time to time,” said the official. “We have not imposed any ban on exports of vaccines, unlike many other countries.”

New Delhi suspended exports after a wave of what critics described as “vaccine nationalism”. The EU and Britain have squabbled over supplies while Italy blocked the export of 250,000 doses of the Oxford/AstraZeneca vaccine to Australia at the start of March.