The UK’s chief medical officers warned of vaccine shortages for months as they defended a strategy to delay the second shots of its Covid-19 immunisation programme. Britain decided to give as many people as possible the first of two jabs to try to ensure partial immunity to tackle the fast-rising number of coronavirus cases at the start of 2021. The UK was the first country to approve the Pfizer-BioNTech vaccine, which was followed this week by the regulator passing the cheaper University of Oxford-AstraZeneca treatment that the government said would be a game-changer for the programme. But authorities decided to delay second doses by up to 12 weeks to stretch current supplies, a decision criticised by the main UK doctors’ organisation as “grossly unfair” for at-risk patients at the front of the queue. “We have to ensure that we maximise the number of eligible people who receive the vaccine,” said the chief medical officers of England, Wales, Northern Ireland and Scotland in a joint statement. “Currently the main barrier to this is vaccine availability, a global issue, and this will remain the case for several months and, importantly, through the critical winter period ... vaccine shortage is a reality that cannot be wished away.” More than one million of the UK's 66 million population have received the first Pfizer vaccine dose and a very small number received a second after 21 days. The medical officers said they recognised re-scheduling second appointments would be “operationally very difficult” and would distress patients expecting to be fully immunised. But they said about 30 million people in the first phase of the vaccination programme were unprotected and a single dose could provide at least 70 per cent protection. “These unvaccinated people are far more likely to end up severely ill, hospitalised on in some cases dying without vaccine,” they said. Concerns are mounting about the effect on the overstretched National Health Service with mothballed field hospitals constructed in the early days of the pandemic being readied again for patients. The Royal College of Nursing’s England director, Mike Adams, told Sky News that it was infuriating to see people not following the social distancing guidance or wearing masks. New infections more than doubled in recent weeks after a new variant thought to be about 70 per cent more contagious was found to be behind a big surge in cases around London and the south-east of England. Given the lag between new cases, hospital admissions and subsequently deaths, there are huge concerns about the path of the pandemic over the coming month or two in a country that at almost 74,000 has Europe's second-highest virus-related death toll.