The Brazilian and South African coronavirus variants are of more concern than the UK strain, the UK's chief scientific advisor has warned.
Sir Patrick Vallance said fears have been raised that those two variants may be 'less susceptible to vaccines'.
Speaking at a Downing Street press conference on Friday afternoon, Sir Vallance said: "We know less about how much more transmissible they are.
"We are more concerned that they have certain features that they might be less susceptible to vaccines.
“They are definitely of more concern than the one in the UK at the moment, and we need to keep looking at it and studying it very carefully.”
It comes after Health Secretary Matt Hancock said “there is evidence in the public domain” that the South African coronavirus variant “reduces by about 50 per cent” vaccine efficacy.
In what is reportedly a recording of an online webinar with travel agents this week, obtained by MailOnline, Mr Hancock said: “There is evidence in the public domain, although we are not sure of this data so I wouldn’t say this in public, but that the South African variant reduces by about 50 per cent the vaccine efficacy.”
He added: “We’re testing that and we’ve got some of the South African variant in Porton Down, and we’re testing it. We’ve got a clinical trial in South Africa to check that the AstraZeneca vaccine works.
“Nevertheless, if we vaccinated the population, and then you got in a new variant that evaded the vaccine, then we’d be back to square one.”
Meanwhile, Sir Patrick Vallance said evidence is growing from multiple sources that vaccines will work against the UK coronavirus strain.
Sir Vallance confirmed that the strain, which emerged in Kent, is “a common variant comprising a significant number of cases” and transmits up to 70pc more easily than the original virus.
He told the Downing Street briefing: “There’s increasing evidence from laboratory studies that the variant in the UK will be susceptible to the vaccines.
“There’s increasing confidence coupled with a very important clinical observation that individuals who have been infected previously and have generated antibodies appear to be equally protected against original virus and new variant.”