After cases of the Indian variant more than doubled in the past week, the prime minister told a Downing Street press conference on Friday that the four-step “road map” we will move to step three in England from Monday as planned – be he raised the possibility of altering the final stage.
The PM said: “But I have to level with you that this new variant could pose a serious disruption to our progress and could make it more difficult to move to step four in June.
“I must stress we will do whatever it takes to keep the public safe.”
At the briefing, chief medical officer Chris Whitty said there is “now confidence” that the India variant is “more transmissible” than the strain first discovered in Kent.
It is expected that the Indian variant will overtake Kent to become dominant in the UK, though there is currently no evidence to suggest vaccines do not work against it.
Johnson said that if the Indian variant proves to be “significantly more transmissible” than other Covid strains “we’re likely to face some hard choices”.
In recent days, the government has launched a series of measures in a bid to dampen any impact from the Indian variant.
The latest is people over 50 and the clinically vulnerable being offered their second dose of a Covid-19 vaccine eight weeks after the first – rather than 12.
The variant is now in at least 15 areas of England – including Bolton, Blackburn, London, Sefton and Nottingham – where councils and Public Health England officials are working to contain any clusters.
This includes surge testing, encouraging people to isolate if they test positive and longer opening hours at vaccination centres.
Johnson said that if the variant turned out to be much more transmissible than other variants, the country could face “hard choices” as he warned of the need to be “utterly realistic”.
He said: “This doesn’t mean that it’s impossible that we will be able to go ahead with step four, I don’t think that’s the case at all. But it does mean there is now the risk of disruption and delay to that ambition. And we have to be utterly realistic about that.”
This article originally appeared on HuffPost UK and has been updated.