Speaking at an NHS England webinar for primary care staff on 8 April, Dr Nikki Kanani reiterated earlier warnings that UK supply will be limited this month - with the vaccination campaign expected to be focused largely on second-dose vaccinations.
She told the webinar: 'We do have reduced supply over the coming weeks, which is why there are no new first dose deliveries on the week of 12 April or the week beginning 19 April.'
GPonline reported earlier today that in the first seven days of April, 71% of doses of COVID-19 vaccine administered in the UK have been second doses.
Health and social care secretary Matt Hancock said last month that some first doses would be delivered in every week of April - although numbers of first-dose vaccinations look set to drop well below the 94,240 delivered per day on average in the first seven days this month.
Responding to a question in the webinar about vaccinations for patients aged under 30 - who will now be offered an alternative to the Oxford/AstraZeneca vaccine if they have yet to receive a first dose - Dr Kanani reiterated advice that second doses should go ahead with the same vaccine as planned.
Asked how vaccination sites should respond if patients under 30 who had received a first dose of the AstraZeneca vaccine asked for a second dose of a different vaccine, Dr Kanani said: 'We are trying really hard not to do that. We are really keen that unless clinically indicated we do not give an alternative.'
NHS England medical director for COVID-19 vaccination Dr Jonathan Leach added that although research was underway, there was currently no clinical evidence available about the implications of mixing vaccines and the impact this could have on protection against COVID-19.
NHS England director of primary care vaccination Dr Caroline Temmink told the webinar that with supply of vaccine for first doses extremely limited in the coming weeks, vaccination sites should consider whether they could use 'residual vaccine from some of your second-dose allocations' for patients aged under 30.
Where patients aged under 30 in Joint Committee on Vaccination and Immunisation (JCVI) cohorts 1-9 were booked in for a first dose of the AstraZeneca vaccine and had their appointments cancelled in light of updated advice from the MHRA and JCVI, spare second-dose supply could be used to offer this group a first jab, she explained.
Practices should also consider sending patients to other local sites with spare doses if they had none themselves - and NHS England will issue advice in the coming days about securing 'baby boxes' of Pfizer vaccine to support first doses in small numbers of patients aged under 30 in the coming days.