Pediatrician Matthew Davis, M.D. explains how immunizations work:
Vaccination protects against illnesses in two main ways. First, the person being vaccinated is protected, because the vaccine stimulates his or her immune system to recognize the harmful bacteria or virus in the future and provide a protective response. This is the process of being “immunized.” Vaccines are developed to provide the benefits of im munization as effectively as possible to all people who receive them, while producing as few side effects as possible. However, just as people vary in the benefits they get from prescription medicines, people also are different in their immunity from vaccination. Many people get maximum benefit while some not as much. In addition, protection from vaccination can decrease over time. Doctors call this “waning immunity.”
That’s what makes herd immunity — the second form of protection from vaccines — so important. Just as a herd of animals will form a protective circle around its most vulnerable members, herd immunity refers to how well immunized people in a community protect the less- or nonimmunized people in that same community. This is an extremely important benefit of vaccination programs, because not everyone can receive vaccines, for medical reasons, and because some people who have been vaccinated will not fully respond.
Immunization is not an individual enterprise. Herd immunity can only be achieved if everyone is immunized. A person’s refusal to be immunized affects everyone. This is why there are rules about immunization and attending public schools.
Caveat: There are side-effects
We must state unequivocally that there are side-effects of vaccines. One of the most dramatic although rare reactions is a seizure. Child seizures are very difficult to watch. The good news is seizures caused by the MMR vaccine is less frequent than seizures caused by the measles, the disease the vaccine is designed to prevent.
Why so many vaccines at the same time?
Children are given a large amount of vaccines because they are the most susceptible to disease during their early years. “There is no scientific data suggesting a medical benefit from spacing out vaccines over a longer period than the official recommendations” according to the magazine Scientific American.