Pharmacists and GPs are being 'strongly encouraged' to continue vaccinating as many people as possible against flu, due to low levels of uptake.
Public Health England (PHE), which issued the call, noted vaccination clinics had started later than normal this flu season due to manufacturing problems with the nasal spray for children and a delay in the World Health Organization’s recommendation on influenza strains.
PHE stressed vaccinations needed to continue over the coming weeks, despite this usually being a period when vaccination activity slows.
It follows an alert sent out by PHE's London team encouraging children to get vaccinated, after it revealed only 19% of pre-school age children in the city had received the vaccine - half the rate for the UK.
Since the start of the season, 23 flu outbreaks have been reported in London, mostly affecting schools.
Dr Jamie Lopez Bernal, head of flu at PHE, said: 'Although flu shows signs of peaking, it is still circulating in the community.
'Anyone who is eligible and has not yet been vaccinated should contact their GP or pharmacist without delay.
'Uptake among two to three-year-olds is behind where we would like to see it, so we are calling on parents to get their children vaccinated as soon as possible.'
He added: 'Current evidence suggests the vaccine is a good match for the main strain of flu that is circulating.'
In its weekly report, PHE said: 'PHE and NHS England are strongly encouraging GPs and pharmacies to continue to vaccinate as many people as possible, as uptake remains lower than last year.'