The shortage of supplies is expected to last during April, and the NHS has written to local health organizations urging them not to take any new appointments for vaccinations from the 29th of March.

Those who already have bookings are not expected to lose their slot.

The BBC has been told that fewer batches of AstraZeneca vaccines are available than expected.

Despite that, ministers insist that the vaccination targets they set are still achievable.

And during the day, the Department of Health announced that 25 million people have now had their first jab.

As our political editor, Laura Coons.

Berg tells us every jab, another step towards the way out every injection, part of what the government seen as a huge success, not far off half the adult population, with now some protection against covid.

I've got some fantastic news to bring you today news The health secretary was happy to share.

We have now vaccinated over 25 million people.

The vaccine is our way out.

We are on track, so let's stick with it.

Follow the rules and when you get the call, get the jab.

Perhaps the journey is less smooth than we might have assumed.

A letter from the NHS to local trust says volumes for first doses will be significantly constrained because there's a reduction in national inbound vaccine supply services should close unfilled bookings from March the 29th and not look any further appointments for April.

You've just told everybody that we are on track with the vaccination, but you haven't mentioned this letter from the NHS, which says that there is a significant reduction in the available supply and vaccine centers should stop taking appointments for the whole month of April.

What is going on?

Vaccine supply is always lumpy, Uh, and we regularly send out technical letters to the NHS to explain the ups and downs of the supply over the future weeks.

And what you're referring to is a standard one of those letters, I'm told.

This is not just a standard glitch.

Sources suggest fewer AstraZeneca vaccines are available than the NHS expected.

So as the opposition convinced by the government's explanation now, now, now he's putting a positive spin on it there that this is a month long pause of appointments.

This is a more significant disruption then we've had so far in the last three months.

Uh, and there may well be an entirely reasonable explanation.

We just need those details tonight.

And look who popped up with another blast for the health department today.

You're missing being part government.

The prime minister's very much former chief advisor, Dominic Cummings, surfaced, giving evidence to MPs order order.

The committee suggested the Department of Health had stumbled badly at the start of the pandemic and hadn't been capable of running the vaccine program itself.

It's not coincidental the vaccine program worked the way that it did.

Um, it's not coincidental that to do that, we had to take it out of the Department of Health in Spring 2020.

You have a situation where depart for health was just a smoking ruin in terms of procurement, and importantly, no one with a vaccine booked should miss their chance.

No one waiting for their second job should lose out either.

Nine far, but so much of Boris Johnson and the country's hopes are based on the vaccine.

Any slowdown causes nerves.

Laura Ginsberg, BBC News Westminster with me in the studio health editor Hugh Pym.

What's going on with supplies?

You?

Well, you.

It appears to be an issue surrounding AstraZeneca's international supply chain doses.

Coming into the UK it's a complicated business.

It can involve independent suppliers and contractors.

The company's made clear tonight that its domestic supply arrangements are not affected.

But there is, as we've been hearing, a significant reduction from early April onwards.

Health officials are saying, though, that their targets that's getting the top nine priority groups, including those age 50 and over in the clinically vulnerable, all offered the first dose by the middle of April.

That is on track, we're told, and the overall target of all adults being offered it by the end of July.

But the big difference is GPS and other vaccination clinics have been told.

Don't send any letters out to anyone aged under 50 for the whole of April.

Pause that so that side of things is going to be delayed.

Certainly by a few weeks we've often discussed the questioning around how efficient the vaccines are, how they perform, if you like.

We've heard a little more about that today.

Yes, officials at the Downing Street briefing were understandably saying, This remains a very, very successful program.

More than 25 million people offered a first dose who had a first dose so far.

It was said that the new research shows that it cuts transmission by 30% that is, from the vaccinated to those who haven't had the vaccine, 60% reduction was quoted in catching covid amongst the over seventies in a bigger reduction in risk of actually becoming seriously ill.

So that's all very positive.

But I think today's developments are a reminder that making big predictions about what might happen in the months ahead is very, very difficult because supplies can never be predicted that accurately.

Many thanks again, Hugh Pym, our health editor them.

All of which brings us to the latest official figures on the pandemic 5758 new cases recorded in the latest 24 hour period.

That means on average, the number of new cases reported per day in the last week is 5665.

The number of patients in hospital with covid continues to fall is now down to 7218.

There were 100 and 41 deaths reported of people who died within 28 days of a positive covid 19 test.

That means on average, 121 people died every day in the past week from coronavirus taking the total of deaths so far, 225,831.

Let's have a look at the latest figures on vaccinations.

433,320 people had their first dose of a covid vaccine in the latest 24 hour period.

That takes the total of people who have now had their first job past 25 million.

As I mentioned earlier, that means 48% of the UK adult population has now had its first vaccination.

More than 1.7 million people have in fact had both doses of the vaccine, so those are the latest official figures.

The European Union has been dealing with its own vaccine supply problems for some time, with some member states facing the very real threat of a third wave of infections, and tensions have been rising between individual countries and the European Commission or still have underlying who's president of the commission, surprised many today by warning that unless supplies improved, the EU might need to impose limits on exports of vaccines from European factories.

She said that the EU was still waiting for exports from the UK, and she said they wanted reciprocal treatment Are Brussels correspondent Nick Beak has more details in Prague, in Paris and once again in Bergamo in northern Italy, covid patients gasping for air The nightmare prospect of a third wave in Europe is now real.

The continent is also facing a vaccination crisis.

It's not getting the doses it ordered and today are warning that the you would do everything needed to get its fair share.

All options are on the table.

We are in the crisis of the century, and I'm not ruling out any anything for now because we have to make sure that Europeans are vaccinated as soon as possible.

Officials in Brussels have faced heavy criticism over their vaccine program and have now come out fighting.

The EU says it sent millions of doses to the UK in recent weeks but seen little in return from AstraZeneca.

But remarkably, seven million of the company's jabs are sitting in fridges and its use has now been suspended in most EU countries.

It's still available here in Belgium, but increasing numbers are saying they don't want the AstraZeneca shot.

I'm not sure that it will be okay if it's as for for old people, so then that's why I know.

I'm afraid Everybody is afraid of this vaccine.

The use medicine regulator is assessing the latest evidence from a very small number of cases of a possible link to blood clots.

But it stresses the benefits outweigh the risks, a message amplified in today's Downing Street press conference.

Vaccines don't save lives if they're in fridges, they only save lives if they're in arms and that's a really important fact.

All medicines have side effects and all medicines have benefits.

And that's the whole point.

That absolute confidence in the AstraZeneca vaccine is now very hard to find in many European capital cities.

But still, the EU is adamant it should get all of the British made doses it's ordered and has now raised the heat in this latest post Brexit row.

And this evening the government condemned the use action, saying it was wrong to threaten even tighter controls on vaccine exports.

I'm surprised we're having this conversation is normally what the UK and the EU team up with.

Two.

Object when other countries with less democratic regimes in our own engage in that kind of brinkmanship, it is a deepening rift and will do nothing to ease Europe's resurgent covid crisis.

And there is growing concern that the rise in new cases, the shortage of vaccines and the reluctance to take the ones that are available could be a deadly combination.

And that is why already, some countries have been tightening their lockdown measures to try to fight a third wave here in Europe, it all feels pretty uncertain.

Hugh.

Tomorrow, all eyes will be on the use medicines regulator when it gives its latest assessment on the safety of the AstraZeneca vaccine.

Nick more from you tomorrow.