The U.S. health authorities require that all children be vaccinated against measles; otherwise they will not be admitted into public schools, nurseries or any day care centres.
Parents who do not respect these laws can risk paying fines and even jail sentences.
If they intend to register their children in school or kindergarten, they are now compelled to show evidence that their children have indeed been vaccinated with MMR (mumps, measles and rubella).
The reason some parents are reluctant to have their children vaccinated is for fear of consequences related to asthma, autism and other deficit hyperactivity disorders.
All children must have had two injections of the MMR vaccination if they want to enter schools or kindergartens.
As a result of these restrictions up to 98% of U.S. children are immunised, while in the United Kingdom only 78% of the children are.
Last year in the United Kingdom there were 1,348 cases of measles as opposed to only 70 cases in 2001, the disease has become widespread throughout the country, while only 135 cases were declared in the whole of the U.S.
These results are encouraging for the U.S. and the CDC declared that the vaccination requirement for registering in schools was the only way to ensure that most of the children would actually receive the vaccination.
Officials however are still worried that the non-vaccinated American children may risk catching measles when on holiday abroad, and bring it back into the country.
Notwithstanding the regulations, there are exceptions for the MMR vaccination, in cases of medical problems or religious beliefs.