What are the pros and cons of mandatory immunization (like DPT, measles, mumps and Rubellla)?
The pro list for mandatory immunizations is quite easy- they prevent disease. The diseases that you mention in your question are good examples; all of them are quite infectious, and all of them are capable of inflicting serious and permanent harm. The eradication of smallpox could never have been accomplished without mandatory immunization. Vaccination is also considered to be a good financial investment, as the cost of immunization is much smaller than the net costs to individuals and society of the diseases and their effects.
On the con side, immunizations have become quite controversial in recent years. Most vaccines can cause side effects, including giving the recipient an allergic reaction or a mild case of the target disease. Many vaccines used to be preserved with the mercury-containing compound thiomersal, which has been blamed for a wide variety of problems including autism. Subsequent research has shown no such link, but parents still fear this possible side effect.
Refusal of vaccinations has repeatedly been held out as an example of personal liberty and choice. There are also some religious groups that avoid modern medical interventions, including vaccination, as a matter of doctrine.
Some pros for mandatory immunization, for having a child vaccinated is it will prevent them from getting DPT, measles, mumps and Rubellla and further endangering others around them. Epidemics are started by those who have not been properly vaccinated.
Some cons to mandatory immunization, which I never realized til this century, is that some people have claimed it causes autism. Others do not.
Another con is that it might and this is rare, make the child sick. The vaccine might not prevent the child from getting one of the diseases. But this rarely if ever happens.