Experts have called for greater clarity about the monitoring in place to assess the 12-week dosing interval for Covid vaccines, as the UK’s vaccination programme ramps up. According to government data released on Sunday, a total of 6,353,321 people in the UK have received at least one dose of a Covid vaccine. A further slew of vaccination centres are due to open on Monday to speed up delivery of the jabs. These include at the Crick Institute in London, the Blackpool Winter Gardens, Lancaster town hall, Bath racecourse and the Black Country Living Museum, where scenes for the TV show Peaky Blinders were filmed. “These 33 new major vaccine centres will bolster our existing network and enable the NHS to protect as many people as possible in the coming weeks,” said the vaccine minister, Nadhim Zahawi. However, there is continued controversy about the government’s decision to increase the interval between the two doses of the jabs to up to 12 weeks in an effort to offer protection to as many people as possible. While there is some evidence from trials that a 12-week gap does not reduce the efficacy of the Oxford/AstraZeneca vaccine, Pfizer has said it has no data on whether protection after the first dose is sustained beyond three weeks. The British Medical Association is among those voicing concerns, saying the gap between doses of the Pfizer/BioNTech jab should be reduced to six weeks. But others have defended the shift towards a longer interval, saying it is evidence-based and is the best option once the risks and benefits are weighed up. Prof Anthony Harnden, of the Joint Committee on Vaccination and Immunisation (JCVI), said the committee believed the approach was the right way forward. “Hopefully not only will this strategy get more people immunised and protect the vulnerable elderly and save thousands and thousands of lives, it may in the end give protection to the population as a whole,” he told Sky News on Sunday. Harnden added that data from the Moderna vaccine, which is based on a similar approach to the Pfizer/BioNTech jab, produced 90% immunity in participants two months after receiving one dose. The comment could be a reference to a JCVI document that showed the efficacy of the Moderna jab reached 80% among almost 1,000 people followed up between one and 108 days after their first dose, and just over 90% when assessing Covid cases at least 14 days after the first jab. However, the document urged caution. “There appears to be some protection against Covid-19 disease following one dose; however, these data do not provide sufficient information about longer term protection beyond 28 days after a single dose,” it stated. The British Society for Immunology (BSI) said that while it accepted the rationale for the 12-week dosing interval in the current circumstances, there needed to be greater clarity about how the potential effect of this interval was being assessed, noting that while Public Health England had published a Covid-19 vaccine surveillance strategy, details about how the immune response is to be monitored remained unclear. “We are assured studies are ongoing, but whether they are the types of studies as a body of immunologists we’d like to see there is still a question mark,” said Dr Doug Brown, the CEO of the BSI, adding that such studies were important in order to explore how best to use the vaccines now and in the future. Others have gone further, calling for large randomised control trials to be set up to explore how different dosing schedules might affect issues ranging from the long-term effect on Covid-related hospital cases to the potential impact on long Covid. While the UK’s vaccination programme continues to expand, concerns have been raised that distribution around the country is far from equal. According to figures from NHS England, the Midlands has so far delivered more than a million first doses of Covid jabs – the first region to do so – with the north-east and Yorkshire hot on its heels with 905,794 first doses administered. However, London continues to lag behind all other regions, having delivering just 586,559 first doses so far. Last week the mayor of London, Sadiq Khan, told the Guardian that “the government’s original distribution formula meant that London missed out on its early fair share of the vaccine”. However, despite Khan saying Zahawi had promised supply and distribution would increase, the Department of Health and Social Care later cast doubt on plans to change the distribution formula. “Vaccines are being distributed fairly across the UK – including London – to ensure the most vulnerable are immunised first, and all GPs will continue to receive deliveries as planned,” it said.