Health officials in Lancashire have blamed a second measles outbreak on parents refusing to vaccinate their children against the illness.
Vaccination rates in the outbreak area are as low as 30%
There have been nine cases since the beginning of October in Accrington, while a month earlier there was an outbreak of similar size in nearby Burnley.
Cumbria and Lancashire Health Protection Unit (HPU) said only 30% of people had vaccinated their children against measles in the area of the town where the latest outbreak has emerged.
It has reiterated its advice that there are no health risks associated with the MMR vaccine.
Dr John Astbury, of the HPU, said he feared the disease could become endemic in the county if more children were not vaccinated.
Dr Astbury said: "There's been a small outbreak of measles in a vulnerable community in east Lancashire.
"We know that in this community the uptake rate of vaccination is only about 30% and it has great potential to spread.
"We're encouraging anybody who hasn't been vaccinated to consider vaccination.
"To stop an infection travelling in the community we do need 90 to 95% of children to be vaccinated.
"We are getting cases spreading out from the initial centre of it and the sort of vaccination levels that we're seeing now means there is potential for measles to become endemic in this area particularly among the younger age group."
'Not benign illness'
Dr Astbury added: "The fall in vaccination rates are directly caused by the controversy over MMR - there's a clear link between the fears of autism and this outbreak.
"I think the debate [over MMR safety] is largely over. There's no good evidence to support that the measles vaccine does produce autism - there's only one paper supporting that view and there've been numerous papers disputing that view.
"Measles is not a benign illness, it kills about one in every 2,500 who gets it and it can produce hepatitis and pneumonia among other side effects."
The triple vaccine MMR is intended to defend children against measles, mumps and rubella.