The proportion of five-year-olds having both MMR jabs in Calderdale is below target despite a rise in immunisation rates.
The latest Public Health England figures for 2017-18 show that 93.1 per cent of five-year-olds had received both MMR jabs before their fifth birthday, up from 91 per cent the previous year.
This still means that 70 five-year-olds in the area are unprotected against highly-contagious measles.
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The target, set by the World Health Organisation, is 95 per cent coverage.
Experts have said that the uptake of the jab across England, where 87.2 per cent of five-year-olds have had both jabs, is "worryingly low".
The MMR jab is a three-in-one vaccine for measles, mumps and rubella. It is given to young children in two doses - the first at 12 months, and the second around three years.
The Royal College of Paediatrics and Child Health and the British Society for Immunology are concerned about children getting the first jab, but not the second.
Of the 2,832 five-year-olds living in Calderdale, 2,762 had the first MMR jab, and 2,636 had both jabs.
That means that in addition to those with no protection, 126 children missed out on the second dose of MMR and will only be partially protected.
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One in 10 children will not be protected against measles after the first dose alone. After the second, that falls to one in a hundred.
BSI chief executive Dr Doug Brown said: "One in 10 people unprotected simply just isn't good enough."
This year there have already been 876 confirmed cases of measles in England, more than three times the number recorded in the whole of 2017.
Although measles is now more common in teenagers and young adults, Dr Brown said that it's more important than ever to make sure young children are fully protected.
He said that reduced uptake rates were "disappointing".
"If we are in a position of increased outbreaks, low immunisation is even more worrying," he said.
Dr Brown added: "Vaccination is one of the few miracles of modern medicine. It is one of the safest and most cost-effective methods we have to prevent the spread of disease."
The Royal College's immunisation expert Dr David Elliman said that a lack of awareness around the importance of getting both jabs, rather than a decision by the parents, could be causing children to miss the second dose.
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Dr Elliman said: "The best solution is GPs sending regular reminders to parents, and all GPs should make sure they have an efficient reminder system in place."
He added that anyone who has missed the MMR vaccine can still get it for free at their GP.
"But even healthy children can get nasty measles and die from it," he added. "A third of measles cases will end up in the hospital."
Public Health England said that they are working closely with the NHS and general practice staff to improve uptake.
PHE's Dr Michael Edelstein said: "We are seeing small reductions in uptake for most of the childhood vaccines, which is why we continue to encourage all parents to get the best protection for their children by ensuring they are fully immunised."
The British Society for Immunology is calling on the Government and the NHS to conduct a review of immunisation rates, to learn from the areas that are doing well and apply that to the rest of the country.