It comes after it was revealed that people aged over 40 in the city could be invited to book their Covid vaccination from within days.

Prof Mike Holmes, chair of Nimbuscare which runs the vaccination site at Askham Bar, said people aged 40 to 49 in cohort 10 may be invited to book their jabs from April 15.

He also sought to reassure people about the AstraZeneca jab after news that people aged under 30 with no underlying health conditions should be offered a different vaccine.

He told City of York Council's outbreak board that the odds of dying as a result of a blood clot after receiving the AstraZeneca vaccine are one in one million - compared to the death rate from Covid in York which is 1.5 deaths per 1,000 people who test positive for the virus.

"That just gives us some context," Prof Holmes said. "The absolute risk of thrombosis is low.

"The Joint Committee on Vaccinations and Immunisations guidance is suggesting that we should continue to get AstraZeneca unless you are under the age of 30 with no underlying health conditions in which case you should be offered a choice of alternative."

People aged under 30 with no underlying health conditions are not set to get the vaccine yet.

Prof Holmes said 40 to 49 year olds are due to start getting vaccinated from late next week and that it may not be until late May or early June that 18 to 30-year-olds are called up for the jab.

They are likely to be offered either the Pfizer or the new Moderna vaccine as an alternative.

The first dose of Moderna was given in Wales on Wednesday.

Prof Holmes said the Moderna vaccine requires patients to stay under observation for 15 minutes after the jab - which is also the case with a Pfizer dose. It is stored at 2 to 8 degrees C and the second dose can be given four to 12 weeks after the first.

Prof Holmes said: "We're discussing with the NHS about offering Moderna from as early as next week.

"We've been in discussions with them over the last week or so and if everything goes well then we should be all be able to offer it next week. There's quite a number of things that we have to put in place, training for staff, the various processes around storage and administration.

"There's more information to come but it's looking positive for next week and certainly by the time we get to the under 30 cohort we'll definitely be able to offer that as an alternative."

More than half of York's adult population have received a Covid vaccine.

Data from April 6 shows 53.6 per cent have had their first dose and 9.3 per cent have had both doses.