MATT Hancock had led the No10 press conference tonight as Boris Johnson is isolating after contact with someone with coronavirus.
The PM had been expected to lead his weekly address to the nation but now has to stay indoors in case he's picked up coronavirus again.
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The Health Secretary stepped in to deliver a Downing Street address this evening.
He appeared alongside PHE’s Dr Susan Hopkins and deputy chief medical officer Jonathan Van Tam - and announced that the UK has bought 5million doses of the new Moderna vaccine - which was found today to be 94 per cent effective.
The PM will continue to work from No10 this week and currently has no symptoms.
In an upbeat video posted to Twitter this morning, Mr Johnson declared himself "bursting with (coronavirus) antibodies" after contracting the virus in April.
"It doesn't matter that I'm fit as a butcher's dog, feel great...that I've had the disease and I'm bursting with antibodies," he said
But he assured Brits he would follow NHS advice and self isolate for 14 days after seeing MP Lee Anderson, who tested positive for Covid-19 over the weekend.
While Mr Johnson is unable to hold the coronavirus briefing, Mr Hancock will front up to the nation.
The Health Secretary told BBC Radio 4 it was crucial the PM follow the rules as it was possible people can catch coronavirus twice.
He said: "The answer is because some people do get it again.
"I've had it but I follow all of the rules because people can catch it twice.
"We haven't yet got the rigorous evidence we need on how likely people are to catch it twice, although we are working very hard on that.
"The Prime Minister is following exactly the same rules as every other person in the country."
Asked if Mr Johnson would be able to take part remotely in Commons events, including PMQs, a Number 10 spokesperson said: "I think that's what they are trying to work through."