Thousands of children in Blackpool have been left unprotected from measles over the last decade, figures show.
Unicef said increasing numbers of youngsters are being left at risk.
According to the charity, vaccination rates are plummeting, with misleading anti-vaccination messages on social media thought to be among the reasons.
Public Health England figures show between April 2010 and December 2018, 788 children had not received their first vaccination against measles, mumps and rubella by the age of five.
Two jabs are required by the age of five to provide full immunity, and a further 1,346 children did not receive the second jab.
It means that the overall vaccination rate over the period was 85.6 per cent, significantly below the 95 per cent the World Health Organisation says is needed to prevent the disease spreading.
There were 966 measles cases in England in 2018, up from 259 in 2017.
Measles is highly contagious. The symptoms are unpleasant, including a rash and fever, and there can be serious complications in some cases.
Health Secretary Matt Hancock recently said he would not rule out banning unvaccinated children from schools, as has been attempted in countries including the US and France.
Mary Ramsay, Public Health England’s head of immunisations, said: “The overall risk of measles to the UK population is low. However due to ongoing measles outbreaks in Europe, we will continue to see cases, particularly in unimmunised individuals.
“Measles can be extremely serious, so make sure you and your family are protected.”