The prime minister’s comment came ahead of a meeting of the Scientific Advisory Group for Emergencies (Sage), which will reportedly discuss the issue on Thursday.
Although infections in England are now at their lowest levels since August, Mr Johnson said new variants “pose a potentially lethal danger” to the country.
Asked about the schedule easing of lockdown restrictions should go ahead, Paul Elliott, an epidemiologist at Imperial College, said: “It is a difficult question because we have low levels of prevalence in the community, and we’ve got low levels of disease in hospitals and deaths, so that’s good.
“But I think that the patterns in the Indian variant are cause for some concern.”
Meanwhile, India continues to suffer from a devastating second wave of the virus, with 362,727 new Covid-19 infections and 4,120 more deaths reported on Thursday.