Toddlers in some parts of Liverpool may be at risk of developing deadly unprotected diseases.
A surprising map shows that in many areas of the city, as many as three out of 10 children have not received the first dose of MMR injections on their second birthday.
The vaccine protects against measles, mumps and rubella, a disease that can have fatal complications.
Health experts recommend that 95% of people be vaccinated against disease – people who cannot or will not get jab will then be protected by "herd immunity."
But in some areas such as Dovecot, Toxteth and Greenbank, nearly two-thirds of children have received the first dose of vaccine on their second birthday.
This places unvaccinated children at a higher risk of catching the disease, which can also cause amputation and deafness.
And many larger parts of the city are far from the 95% target according to the map, part of the council's documents.
The report, from the city's director of public health, read: "Currently about 9 out of 10 children are fully vaccinated with the two MMR doses they need on their fifth birthday in Liverpool, and we need to improve this and discuss variations in vaccination taking in the whole city.
"Although absorption is generally high, there are pockets where immunization is low, related to deprivation."
The MMR vaccine was at the center of a scandal in 1998 after now discredited research suggests there is a connection between vaccines and autism.
Even though this research is completely withdrawn, the use of the MMR jab often lags behind the target – and the council says the poverty rate also affects how many people in the community get the vaccine.
On November 22, people affected by measles in Liverpool related to unvaccinated people traveled to European countries where the disease was more common.
Five hundred children in the area were vaccinated after the outbreak and no one died.
In order to be fully vaccinated against children with measles, mumps and rubella are recommended to get two injections – one around their first birthday and one before they start school.
There is also a pursuit program for older children who did not get the vaccine at this time.