Hundreds of new vaccination sites are due to be up and running this week as the NHS ramps up its coronavirus immunisation programme with the newly approved Oxford University and AstraZeneca jab.

Some 530,000 doses of the vaccine will be available for rollout across the UK from Monday, with vulnerable groups already identified as the priority for immunisation.

The jab will be administered at a small number of hospitals for the first few days for surveillance purposes, before the bulk of supplies are sent to hundreds of GP-led services to be rolled out, according to NHS England.

Hundreds of new vaccination sites – at both hospitals and GP-led services – are due to launch this week, joining the more than 700 already in operation, NHS England added.

Oxford University Hospitals NHS Foundation Trust, where the vaccine was developed, is expected to be among the first sites to administer it on Monday morning.

Five other hospital trusts, in London, Sussex, Lancashire and Warwickshire, will also start delivering the vaccine on Monday ahead of the wider rollout.

It comes almost a month after rollout of the vaccine developed by Pfizer and BioNTech began, with more than one million people having now received their first dose.

Second doses of either vaccine will now take place within 12 weeks rather than the 21 days that was initially planned with the Pfizer/BioNTech jab, following a change in guidance which aims to accelerate immunisation.

Writing in the Mail on Sunday, deputy chief medical officer Professor Jonathan Van-Tam said this dosing regimen will “save the most lives and avoid the most hospital admissions”.

He said: “If a family has two elderly grandparents and there are two vaccines available, it is better to give both 89% protection than to give one 95% protection with two quick doses, and the other grandparent no protection at all.

“The virus is unfortunately spreading fast, and this is a race against time.

“My mum, as well as you or your older loved ones, may be affected by this decision, but it is still the right thing to do for the nation as a whole.”

Professor Robin Shattock, from the Department of Infectious Disease at Imperial College London, told BBC News there was evidence to support delaying a second dose of the jab from Oxford/AstraZeneca jab.

But he added: “The evidence for the Pfizer vaccine is less robust. It’s only for three weeks, we don’t know what level of protection a single dose might give over a period of up to 12 weeks.

“The potential risk is, if it’s a sub-optimal immune response, although it may reduce hospital admissions, it may give the virus a window to evolve mutations that may render the vaccine less efficacious in the future.

“So it’s really a judgment call. There’s no obvious right decision and people are trying to make the right balance over preventing the hospitals continuing to have high numbers of cases, versus the risks of not going for the full regime in the shortest possible time.”

The Oxford/AstraZeneca jab is easier to transport and store than the Pfizer/BioNTech vaccine, which needs cold storage of around minus 70C.

Prime Minister Boris Johnson hailed the jab as a “a triumph of British science”, adding: “From tomorrow, the NHS will start using the Oxford vaccine to give protection against Covid 19.

“We know there are challenges still ahead of us over the coming weeks and months, but I’m confident this is the year we will defeat coronavirus and start building back better.”

Meanwhile, Health Secretary Matt Hancock said: “The vaccine is our way out and this huge achievement brings us a step closer to the normality we’ve all been working hard to reclaim.

“From tomorrow, the British public will begin to receive a second highly effective vaccine, starting with the most vulnerable and frontline care home and NHS staff, another significant milestone in the expansion of the vaccination programme.

“This will be a historic day, and cause for celebration, but it’s vital everyone continues to follow the rules and remember hands, face, space, to keep ourselves and others safe.”