The vaccine, developed by pharma giant Pfizer and his partner Beyond Tech, has been tested on 43 a half 1000 people in six countries, with no safety concerns being raised so far.

England's deputy chief medical officer Jonathan van Tam, said he was hopeful that the first vaccine might be available by Christmas on there would be a much better horizon in his words by next spring.

Prime Minister Boris Johnson said that one significant hurdle had been cleared, but there were several more to go on.

Some experts were keen to point out that this announcement was made on the basis of very early analysis, with the vaccine not yet formally approved.

Our medical editor, Fergus Walsh, reports on the optimism on the caution which greeted today's news.

This is a huge day for science and perhaps the world.

For the first time, a co vid 19 vaccine has been shown to protect against the disease.

Plenty of caution is needed, but the preliminary results of the Pfizer beyond tech trial are highly promising.

There were more than 43,000 volunteers on the trial, which began in July.

Half got the coronavirus vaccine half a dummy or placebo jab.

Interim results showed 94 of the volunteers fell ill with covert 19, nearly all in the non vaccinated group.

As a result, Pfizer says the vaccine is more than 90% effective.

It's such a great there for science and humanity, you know, I've never felt professionally such a moment of joy, and we were just jumping up and down in the shares off Joy for humanity.

Joyful medical advances to put an end to this dreadful pandemic, The vaccine uses a tiny amount of the genetic sequence of the spike protein, which sits on the surface of coronavirus.

Synthetic material, known as RNA, is injected into muscle cells in the arm.

This stimulates the creation of antibodies.

Why shaped proteins which should bind onto coronavirus, preventing future infections?

Killer T cells are also produced.

Thes should identify and destroy cells which have become infected.

Scientists around the world have moved at an extraordinary pace to develop corona virus vaccines.

There are 47 in human trials.

The UK government has advance orders for six of them, including 40 million doses of the Pfizer Beyond tech vaccine.

That's enough to immunize 20 million people as you need two doses, Pfizer says.

By the end of the year, 50 million doses will be available globally, but only a minority will come here to the UK.

The government also ordered 100 million doses of the Oxford AstraZeneca vaccine were still awaiting their results.

It's thought around four million doses will be available here by the end of the year.

At the number 10 press briefing, there was a sense of cautious optimism off a significant moment in the fight against co vid.

I have to say that this is really a very important scientific breakthrough.

I'm certain of that.

But the prime minister said there were several hurdles to clear before the vaccine could be used on.

He urged people not to slacken their resolve.

We cannot let our enthusiasm tonight run away with us folks.

I'm very, very sorry to say this.

It's more vital than ever now that we follow the basics that we wait and see whether this vaccine lives up to its promise we continue with the measures we have in place on.

Many scientists agree that we can't be sure yet if this vaccine is a game changer.

These are very early results.

What we really need to wait for is the longer term follow up of all these participants in the trial toe.

Understand how effective this vaccine is, say 4 to 6 months after receiving the doses, Pfizer will apply for emergency authorization for the vaccine.

If regulators give approval, the first doses could be used here before Christmas.

A small first step towards ending the pandemic on Fergus is with me.

Lots of talk about optimistic theories based on the results on, Of course, lots of talk about being careful and caution.

Where's the balance for you, Fergus?

Well, it's a rare moment, Hugh, that I've been able to sit here throughout this pandemic and give you some really good news.

And that's one of those occasions.

Thes results really are very promising indeed, and they all go well for other coronavirus vaccines that have used the same approach this spike protein to build immunity.

But the results, though promising, are very early.

What I need to know is does the vaccine.

We know it stops people from getting symptoms and falling ill.

But does it go further?

Does it stop all infection completely, including a symptomatic infection that would be hugely important in building up what we call herd immunity Now?

We also don't know how long any immunity will last.

We may need to have booster vaccines on.

We don't have the crucial safety data, given all of those conditions that you just mentioned.

What does the path ahead look like in the next few months?

Well, if it's approved on, that's a big If we might get a few million doses off this vaccine before the end of the year, it needs to be stored at minus 80 degrees, so rollout won't be straightforward.

First in line would be older residents of care homes and care home staff on then the over eighties on frontline health workers on then progressively younger people.

We shouldn't expect this vaccine to change the way we live this winter.

We're not out of the woods yet, but we might finally have found the right path.

Focus.

Many thanks once again, Fergus Walsh, our medical editor there, with the latest thoughts on today's news and for some more reaction.

Let's talk about the financial markets because they climbed.

Following today's announcement by Pfizer in London, the 100 share index closed almost 5% higher, with similar increases across Europe.

Among the companies to benefit were airlines and hotels and travel companies, which have been hit hard by the pandemic.

Our business editor, Simon Jack, is in central London s O Simon.

To what extent was the talk of caution in Downing Street reflected on the financial markets?

Not really it all, Hugh.

I think that caution was not the word euphoria.

We saw some incredible moves in share prices.

Day, the parent company of British Airways, up 26%.

Pub companies like Mitchells and Butlers, up 26%.

EasyJet up 33%.

Incredible moves.

But remember, these are some of the stocks that have been battered the most on the way down by the virus.

The market is, you said, on the whole, was up.

5% of that was because there were some loses the so called to stay at home stocks that have thrived during lock downs, things like, for example, every office workers new best friend, Zoom.

That was down 15% on Accardo, the online delivery company, down 9%.

But overall, the point is, this is about sentiment.

Markets just need to believe that tomorrow is going to be a little bit better than today.

On that delivered, today's news delivered a syringe full of that kind of optimism.

They know that this is not beaten yet, but the point is, it's beat a bull.

That is what the markets were focusing on.

Before long, they'll have something else to worry about.

But today, euphoria.

A very significant day in the financial markets.

Simon Many thanks again, Simon Jack with the latest on what happened on the financial markets today.