How effective is vaccination in the prevention of these common childhood diseases?
Most vaccines work efficaciously though some do not work as effectively all the time in preventing an attack. For example the proper use of vaccines has managed to wipe out smallpox from the face of the earth while diseases such as measles, diphtheria and polio have been brought down to very low levels or nil in the western hemisphere, and this clearly demonstrates the success stories of when vaccines are enforced at a national level. Sometimes a vaccine will not work and reasons hinge on the vaccine itself as well as the child's immune-system. When vaccinations are made mandatory at a national level, everyone in the family, in the community and in the country will be immunized thereby decreasing the possibility of your child getting the infection from someone else. This is termed herd immunity. Chances of immunized individuals infecting others is greatly reduced and therefore members of the public are protected. If enough people have been immunized, people who have not been vaccinated can be protected from a vaccine-preventable disease thanks to the herd immunity.
A large section of the community has to be vaccinated in order to achieve herd immunity which will in turn help decrease the risk of children getting illnesses from someone else. But global travel is not able to blot out the spread of the many cases of rare diseases when non-vaccinated persons travel or come in contact with someone who has been to a country where the disease still exists. To successfully pass on the disease to another non-vaccinated individual or the very young or fragile is highly probable. When herd immunity is in place, this factor will help retard the spread of infections even when vaccines are not 100% effective.