Boris Johnson is expected to announce today that the final stage of easing Covid controls will be delayed.

It comes after a surge in cases of the Delta variant first identified in India.

Here's what we know so far ahead of an announcement later today.

Why are we considering delaying?

Scientists have been pressing for additional time to get more people vaccinated – particularly those in younger age groups – before controls are relaxed.

Studies have shown that people who have received only one dose of the vaccine have significantly less protection against the Delta variant – first identified in India – than those who have had two jabs.

Public health officials believe a delay would also give more opportunity to control the spread using surge-testing techniques which proved successful in Bolton, which was the first Delta variant hotspot in the UK.

With infections and hospital admissions both rising, Prime Minister Boris Johnson said that it was not yet clear to what extent that would feed through into more deaths.

However, in order to ensure the final lockdown lifting was “irreversible”, he said that it may be necessary to give the vaccines “extra legs” in the race against the virus.

How long will this be delayed for?

Anything from between four weeks to indefinitely is what is being reported ahead of today.

Dominic Raab, talking on The Andrew Marr Show, said if the unlocking was to be “irreversible”, they needed to proceed “carefully and cautiously”.

“We don’t want to yo-yo back in and out of measures,” he said.

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What is still waiting to open up?

The Government had hoped to remove “all legal limits on social contact” from 21 June.

It meant there would have been no restrictions on how many people you can meet, either indoors or outdoors.

However, some social distancing rules could remain in place, and the wearing of masks could still be mandatory in some public places.

Nightclubs and music venues were due to reopen and larger events allowed to resume without limited crowds. 

What are the four tests we need to pass before we can reopen fully?

  1.  Vaccine programme continues successfully
  2. Evidence shows that the vaccines are effective in reducing the number of people in hospital and deaths in people who have been vaccinated.
  3. Infection rates do not risk a surge in hospitalisations which would put unsustainable pressure on the NHS
  4. The assessment of the risks is not fundamentally changed by new variants of concern.

What about a third wave?

Well, that's the concern. The Prime Minister has been accused of risking “fanning the flames” of a new wave of coronavirus infections if he lifts lockdown restrictions too quickly.

That's the warning from a scientist advising the Government.

Professor Andrew Hayward, a member of the Nervtag group which advises ministers on new respiratory diseases, said it was clear the country was facing a “substantial” third wave of the disease.

He said the key issue was the extent to which that led to more people becoming seriously ill and requiring hospital treatment.

“We still don’t know how bad it could be,” he told BBC’s The Andrew Marr Show.

How much more transmissable is the Delta variant?

Professor Hayward said it was “extremely worrying” that the Delta variant – which now accounts for 96% of new infections – was proving to be 60% more transmissible than the previously dominant Alpha strain first identified in Kent.

“That is the thing that will drive the speed with which the next wave comes along,” he said.

“I think if we were to open up more that would really fan the flames and lead to this increasing even faster.”

What are the Government doing?

Foreign Secretary Dominic Raab said ministers and officials were monitoring the data in “real time” to determine when it would be safe to open up.

The move has angered some senior Tories, who have said there is no justification for another “catastrophic” delay to so-called “freedom day” when social distancing finally comes to an end.