Public health officials are urging people in at-risk groups to get vaccinated against influenza before the expected increase in infections in the coming weeks.

The call comes with the re-start of the UK’s primary school flu vaccination programme, following a temporary delay in the supply of nasal spray vaccine Fluenz Tetra.

Public Health England (PHE) and NHS England are advising parents of two and three-year olds to protect their children against the illness, which, they say, can be serious and fatal.

Also, those aged 65 and over, children and adults with underlying medical conditions and pregnant women are also urged to get their free vaccine before flu begins to circulate widely.

“The flu vaccine is the best defence we have against what can be a serious and fatal illness, and flu season is just around the corner,” said Dr Mary Ramsay, head of Immunisation at PHE. “If you are in an eligible group, visit your GP or pharmacist as soon possible to ensure you are protected”.

The call also comes as experts warn of severe GP shortages and over-stretched accident and emergency departments across the UK.