The Delta variant of the coronavirus is estimated to be 40% more transmissible than the Alpha variant which caused the latest wave of infections in the UK, the UK Minister of Health said on Sunday.

But people who have received two doses of the vaccine should also be protected against either variant, he added.

“This figure, about 40% more communicable, is indeed the last piece of advice I have,” Health Secretary Matt Hancock told Sky News.

The Delta variant is now the dominant strain in the UK, according to figures from Public Health England.

It was the Alpha variant, formerly known as the Kent variant, that forced the UK to lock down in January.

Hancock said the 40% figure came from the government’s body of science advisers, SAGE.

Concerns are growing over whether the emergence of the Delta variant threatens the government’s tentative June 21 deadline for lifting restrictions on viruses.

Hancock acknowledged that the Delta variant “makes it harder to calculate for June 21”.

“We will look at the data for another week and then pass judgment,” he told the BBC on Sunday, stressing that the government was “absolutely open” to delaying the lifting of restrictions.

The minister nevertheless stressed that those who received two doses of the vaccine should be protected against the disease of the Delta variant.

Public Health England said last month that research showed the double vaccination was also effective against the Kent and Delta variants.

“The best scientific advice I have at this point is that after a jab it’s not as effective against the new Delta variant, but after both jabs it is,” Hancock told the BBC.

Hospitalizations so far have been “largely stable”, with very few hospitalizations after receiving the two doses of the vaccine, he added.

The UK has so far given two doses to more than 27 million people – over 50% of adults – while over 40 million have received a dose.

Hancock said the government was “taking clinical advice” on whether to extend the vaccination program to children over 12, who would play a major role in the spread of the virus. But it would not be mandatory, he added.