That's a day ahead of the scheduled target.

The prime minister praised a truly nationwide effort and said that everybody who'd contributed from NHS staff to volunteers should be incredibly proud.

The success of the vaccination program has led to a growing pressure for a clearer roadmap out of lock down on a return to some kind of normality, including from some of Mr Johnson's own MPs.

Here's our political correspondent Jonathan Blake, lining up in Lancashire for the coronavirus vaccine, some of those getting their first jab today and taking the total number to be offered an injection to 15 million across the UK This country has achieved an extraordinary feat.

In a video posted online, the prime minister confirmed the government had met its target of offering the four most vulnerable groups in England, their first jab by mid February.

It has Bean a truly national UK wide effort.

We've done it together on.

I want to thank each and every person who has helped make it happen.

You could be incredibly proud of the part you've played.

With vaccinations in full flow, the prime minister's promised a road map out of lock down in England a week tomorrow, the 22nd of February.

The government wants schools to open toe all pupils on the eighth of March.

Next, more outdoor recreation is likely to be allowed, followed by more shops being ableto open on finally hospitality venues.

But with the aim now toe offer everyone over 50 their first jab by the end of April.

Some argue a legal restrictions should end by then.

It's completely tied to the roll out the vaccination program on the fact that you will then protecting the most vulnerable people from death and serious disease from co vid from the fantastically successful vaccination program the NHS is undertaking and in the industry's worst affected, there's an urgency to start trading soon.

We think we can open very safely for Easter weekend.

We understand, as I said, that there would be social restrictions in place like the we're in July and we will absolutely administer those to the letter on.

We will ensure that we've got a responsibility for our customers on our staff.

Some conservative MPs are growing increasingly frustrated and want firm commitments from the prime minister about when restrictions will be lifted.

But though Boris Johnson can't ignore the political pressure from his own party, the risks of opening things up too soon seemed to be weighing more heavily.

And for now, the watchword in government is caution.

Until the impact of the vaccines becomes clear, Political opponents will be the first to accuse Boris Johnson of easing restrictions before coronavirus is contained.

This'll lock down has to be the final lock down.

By the way, the strategic age is to do everything we can now, so we don't have to go back into a lock down.

While seizing on the success of the vaccination program so far, the prime minister acknowledged there was much more work to do.

Return to normal is still some way off.

Jonathan Blake, BBC News.

So having reached the first major vaccination target, how does the rollout proceed from here on Who's next in line for the jab?

Our science correspondent Rebecca Morelle reports from Margaret Keenan in December, the first person to be vaccinated toe less than 10 weeks later, 15 million people have had their first dose.

So who will be vaccinated next on when the next stage starts with 65 to 69 year olds?

That's nearly three million people on those with underlying health conditions and estimated seven million.

Next up, it's 2,000,060 to 64 year olds thin the 5,000,050 to 59 year olds.

That's a total of more than 17 million people who'll be offered vaccines by the end of April.

Then for phase two, another 21 million people the rest of the adult population should be vaccinated by the autumn.

More than a million over 65 have already been sent.

Letters this weekend in some areas have even started delivering jabs.

It's an indication off the different demographics off different parts of the country.

Obviously, certain populations will have much higher proportions off those people who are over 70 or who are housebound, and that will take longer.

In my practice in north London, we are vaccinating already.

Those people over 60 and 65 people with some medical conditions are also being invited.

These include chronic lung disease, down syndrome, diabetes, some cancers on morbid obesity.

So how will we know if vaccination is working?

The best place to look is Israel, which is inoculated mawr of its population than anywhere else in the world, and hospitalizations of those who were vaccinated first the over sixties are falling much faster than other groups.

So when could we see an impact in the UK In about a week's time?

We may well see the beginnings of an effect in hospitalizations, particularly in older people, relative to changes in younger people.

It'll be a cases.

It's going to be a little bit less clear, I think, because vaccine doesn't necessarily stop mild cases in the coming weeks, could there be any problems?

There will be some bumps in supply.

With Pfizer overhauling its factory in Belgium, new variants could also pose a problem on booster shots might be needed to improve immunity.

Co vid levels in the UK are still high, but vaccination should soon make a difference, helping us map a path out of lock down.