When a child is born, she usually has immunity to certain diseases. This is a result of the disease-fighting antibodies that have passed through the placenta from the mother to the unborn child. After birth, the breast-fed baby gets the continued benefits of additional antibodies in breast milk. But in both cases, the immunity is only temporary.
Microorganisms can be viruses, such as measles virus, or they can be bacteria.
Vaccines stimulate the immune system into reacting as if there were a real infection. Some parents may hesitate to give their child a vaccine because they are concerned about complications or their child developing the very illness the vaccine is supposed to prevent. Although it's true that some vaccines could have these effects, the likelihood of that happening is very small . Not immunizing your child exposes her to greater health risks associated with contracting the disease the vaccine is intended to prevent. Immunization is one of the best means of protecting your child against contagious diseases.