The United Kingdom’s vaccination programme will not be derailed by a shortfall in the expected supply of doses, Prime Minister Boris Johnson said. A delay in deliveries from India and the need to retest a batch of 1.7 million doses is behind the issues with vaccine supply in April. The problem with a shipment from the Serum Institute of India was blamed on the country's government by the SII chief, although Mr Johnson said Narendra Modi's administration has not stopped any exports. Mr Johnson said: “We have always said that in a vaccination programme of this pace and this scale, some interruptions in supply are inevitable. “It is true that in the short term we are receiving fewer vaccines than we had planned for a week ago, that is because of a delay in a shipment from the Serum Institute – who are doing a herculean job in producing vaccines in such large quantities – and because of a batch that we currently have in the UK that needs to be retested as part of our rigorous safety programme. “As a result, we will receive slightly fewer vaccines in April than in March but that is still more than we received in February and the supply we do have will still enable us to hit the targets we have set.” The over-50s and the clinically vulnerable will still be offered a first dose by April 15, and second doses will be available to about 12 million people in April. Every adult will be offered a first dose by the end of July, as planned, he said. “Our progress along the road to freedom continues unchecked, we remain on track to reclaim the things we love, to see our families and friends again, to return to our local pubs, our gyms and sports facilities and, of course, our shops,” he said. Mr Johnson told a Downing Street press conference “the Indian government has not stopped any export” but “there is a delay … as there is very frequently in vaccine rollout programmes”. It was revealed on Wednesday that <a href="https://www.thenationalnews.com/world/europe/uk-faces-significant-vaccine-shortage-from-end-of-march-1.1186385">Britain faced a "significant reduction in the weekly supply" of vaccines</a> next month, with the shipment from the sub-continent delayed by four weeks. UK Health Secretary Matt Hancock told MPs a batch of 1.7 million doses was delayed because it needed to be retested. Britain's National Health Service was told not to make any further first-dose appointments in April for younger people. The Serum Institute, the world's largest manufacturer of vaccines, said the doses that were scheduled to arrive in the UK were needed for India’s domestic programme. "Five million doses were delivered a few weeks ago to the UK and we will try to supply more later, based on the current situation and the requirement for the government immunisation programme in India," a Serum Institute spokesman said. The shortage comes as President of the European Commission Ursula von der Leyen refused to <a href="https://www.thenationalnews.com/world/europe/who-calls-for-continued-use-of-astrazeneca-vaccine-as-eu-threatens-to-block-exports-1.1186144">rule out blocking exports to Britain of vaccines made on the continent</a>. She also threatened to seize AstraZeneca factories and strip the pharmaceutical company of its intellectual property rights. The bump in UK supply will cause a bottleneck in the coming weeks, with a backlog of people requiring their second injection. People will receive their booster injection as planned, the government said, and efforts will be made to inoculate those remaining from the top priority groups, including over-50s. Younger people will have to wait a month longer than expected to receive their first shot but the government is confident it will meet its initial target of inoculating all adults by the end of July. Mr Hancock told MPs that there "will be no cancelled appointments as a result of supply issues". Asked whether doses earmarked for Britain were held back for India’s programme, UK Communities Secretary Robert Jenrick told the BBC on Thursday: “It would not be right for me to pin blame on any one manufacturer, factory or country – that is not the case. “The manufacturers are working incredibly hard and it is to be expected we’d experience ups and downs along the road.” Mr Jenrick said the UK had less supply of the vaccine available for April but that people requiring their second dose “should have complete confidence” in their appointment going ahead. “The month of April will be different – and it was always going to be – because I think this will be the month that second jabs exceed first jabs,” he said. The supply shortage was revealed as Health Secretary Matt Hancock was delivering a press conference on Wednesday afternoon. “The government's vaccines taskforce have now notified us there will be a significant reduction in weekly supply available from manufacturers beginning in week commencing March 29, meaning volumes for first doses will be significantly constrained,” a leaked letter to NHS operators said. "They now currently predict this will continue for a four-week period, as a result of reductions in national inbound vaccines supply." After talking up the UK’s vaccine drive, Mr Hancock dismissed the revelation in cursory fashion. "We regularly send out technical letters to the NHS to explain the ups and downs of the supply over the future weeks, and what you're referring to is a standard one of those letters," he said. More than 25 million people have received their first dose of a Covid-19 vaccine in the UK, according to government statistics. The rest of the UK's AstraZeneca doses are being produced domestically and the company said there are no supply issues. Pfizer, which produces its vaccine in Belgium, said its deliveries to the NHS are on track.