All adults in the UK aged over 50 have now been offered a first dose of a coronavirus vaccine, paving the way for the next phase of the rollout, the Government has said.

Boris Johnson hailed another “hugely significant milestone” in the programme to protect the country against the disease.

It means the Government has met its target of offering the jab to all of its top nine priority groups, including the clinically vulnerable and health and social care workers, three days ahead of its target date of April 15.

The Joint Committee on Vaccine and Immunisation will shortly set out its final advice for the completion of the programme, expected to begin this week with those in their late 40s.

The announcement comes after Ireland became the latest country to restrict the use of the AstraZeneca vaccine, saying it should not be given to people under the age of 60, amid concerns over possible links to rare blood clotting events.

In the UK, the advice is that it should not be administered to those under 30.

In all, the Government said almost 40 million doses of the Pfizer and AstraZeneca vaccines have been delivered since the rollout began in the UK in December, including 32 million first jabs and more than seven million second doses.

We have now passed another hugely significant milestone in our vaccine programme

In a statement, Mr Johnson said that they remained on course to offer a first jab to all adults in the UK by the end of July.

“We have now passed another hugely significant milestone in our vaccine programme by offering jabs to everyone in the nine highest risk groups,” he said.

“That means more than 32 million people have been given the precious protection vaccines provide against Covid 19.

“I want to thank everyone involved in the vaccine rollout which has already saved many thousands of lives.

“We will now move forward with completing essential second doses and making progress towards our target of offering all adults a vaccine by the end of July.”

NHS England chief executive Sir Simon Stevens said 19 out of 20 over 50s had now received a first jab.

“Thanks to our NHS nurses, doctors, pharmacists, operational managers and thousands of other staff and volunteers, the NHS Covid vaccination programme is without a doubt the most successful in our history,” he said.

“It’s one of our tickets out of this pandemic and offers real hope for the future.”

The announcement comes despite an earlier warning by the NHS in England of a “significant reduction in weekly supply” during April, meaning volumes for first doses would be “significantly constrained”.

Throughout the current month, the health service has prioritised second doses of the Pfizer and AstraZeneca vaccines with a record 475,230 people receiving their second jab on Saturday.

Meanwhile, there is to be a surge in testing in the boroughs Lambeth and Wandsworth in south London following the identification of a number of cases of a variant of the virus first found in South Africa.

Dozens of people were told to isolate after the Department for Health and Social Care said there had been 44 confirmed cases of the strain, with a further 30 suspected.

It came as scenes posted on social media of revellers gathering in Soho, central London, following the latest easing of lockdown restrictions in England were lifted, prompted fears that social distancing guidelines were being ignored.

Chris Hopson, chief executive of NHS Providers, which represents NHS Trusts, said it was still important to prevent the spread of the disease following the “incredible achievement” of the vaccination programme.

“While there is still a way to go with our vaccination programme, we welcome the progress being made, with the jabs due to be rolled out to the over 40s this week and all priority groups now offered a first dose,” he said.

“As we return to pub gardens and sports activities and make our way back to non-essential shops, we must continue do all that we can to prevent the spread of infection and ensure this lockdown will be the last.”