Children should not hug their grandparents “too much” even if they have been vaccinated against coronavirus, England’s deputy chief medical officer has said.

Jenny Harries stressed that the full impact of the vaccines was still not known as she encouraged families to take a “steady course” out of lockdown.

She spoke as parents and children prepared for the reopening of schools on March 8, the first step in Boris Johnson’s plan to lift lockdown.

Hugging between members of different households will largely remain against the Covid rules until step three on the “road map” on May 17 at the earliest, when the government has promised to update its advice on social distancing between friends and family.

Harries acknowledged that children’s mental health has suffered during the pandemic from being away from their friends at school and being forbidden from seeing “significant” family members.

But at a Downing Street coronavirus briefing, she said: “Having got so far down the line with this and now on the road map very, very carefully coming out, I would encourage children not to go off yet, even if grandparents have had their vaccinations, not to go hugging them too much until we are absolutely sure what the impact of that vaccination rollout has been.

“I’m sure it’s going to be positive but we just need to take a steady course out through the road map.”

Harries also attempted to reassure parents and teachers that schools would be safe due to the testing programme the government is planning for when they reopen.

“Parents, grandparents and teachers and other school children can be very assured that schools will be as safe as they can because we are trying to remove infection from that environment,” she said.

“And of course that will have a really positive impact on breaking chains of transmission in communities and in those families.”