Britain's Prime Minister Boris Johnson (R) wearing a protective face covering to combat the spread of the coronavirus, elbow bumps Ismail Patel (L) after Ismail receives his jab, during a visit to a coronavirus covid-19 vaccination centre, the Al-Hikmah Vaccination Centre in Batley, northern England on February 1, 2021. - Britain has set itself an ambitious goal of vaccinating 15 million of the most vulnerable people by mid-February, and the entire adult population by the autumn. A total of 598,389 people in the UK received a first vaccine dose on Saturday, the highest daily figure since the rollout began. (Photo by Jon Super / POOL / AFP) (Photo by JON SUPER/POOL/AFP via Getty Images)
Boris Johnson has said he is "optimistic" people will be able to go on a summer holiday this year.
The prime minister, however, also warned "things have got to be right" in terms of low coronavirus infections and high vaccination numbers in order for Britons to enjoy a summer break.
Speaking during a visit to a vaccination centre in Batley, west Yorkshire, on Monday, Johnson said: "I don't want to give too much concrete by way of dates for our summer holidays.
"I am optimistic - I understand the reasons for being optimistic - but some things have got to go right."
It's not clear whether the PM, who last week set out 8 March as the earliest date lockdown restrictions will be eased, was speaking about holidays abroad or in the UK.
He added: "The vaccine programme has got to continue to be successful. We have got to make sure we don't get thrown off course by new variants, we have got to make sure that we continue to keep the disease under control and the level of infections come down."
There were also encouraging words about summer from a Scientific Advisory Group for Emergencies (Sage) adviser on Monday.
Dr Mike Tildesley, a member of the Scientific Pandemic Influenza Group on Modelling (Spi-M) sub-group, said the UK could be easing out of restrictions in March and back to almost normal by summer if vaccines are 70% to 80% effective at blocking transmission.
He told BBC Radio 4's Today programme: "If the vaccine rollout continues at high levels, and we do find that actually these vaccines are very good at blocking transmission as well as preventing severe infection, then we're in a good position.
"Hopefully by the summer we can get back to something pretty close to what we have seen before the pandemic was normal."
Dr Tildesley said more will be known about the vaccine's impact on blocking transmission within the next month, and that Tildesley a 70% to 80% rate of stopping the virus spreading would "probably [mean] we're in a good place."
Watch: What you can and can't do during England's third national lockdown