Can my child’s immune system handle these diseases by itself?

Short Answer

It’s possible, but it’s not guaranteed. Every child’s immune system works differently, and there’s no way of knowing how effectively a child’s immune system will ward off disease, even in the healthiest children. Some kids have minor symptoms and recover completely, while others suffer serious and permanent damage or death. Newborn babies may receive some temporary protection from their mothers during the last few weeks of pregnancy, but only for diseases to which the mom is already immune. Breast-feeding may also help protect babies temporarily from minor infections, like colds, but not other serious vaccine-preventable diseases. For the best protection, follow the recommended vaccination schedule for babies and children.

Source:

http://www.historyofvaccines.org/content/articles/top-20-questions-about-vaccination#4

http://www.cdc.gov/vaccines/parents/parent-questions.html

Natural immunity occurs when your child is exposed to a disease and becomes infected. In some cases, natural immunity is longer lasting than the immunity gained from vaccination. For example, a child who successfully recovers from chickenpox will most likely be free from reinfection for life, whereas the vaccine may wear off. However, the risks of natural infection outweigh the risks of immunization for every recommended vaccine, as it is far, far less likely for death to result from vaccination. An example of this is evident in the case of measles. A wild measles infection causes encephalitis (inflammation of the brain) in one of every 1,000 cases. Overall, measles infection kills two out of every 1,000 infected individuals. In contrast, the combination MMR (measles, mumps, and rubella) vaccine results in a severe allergic reaction only once in every million vaccinated individuals, while also providing protection from measles infection. The benefits of vaccine-acquired immunity extraordinarily outweigh the serious risks of natural infection. Additionally, the Hib (Haemophilus Influenzae type B) and tetanus vaccines actually provide more effective immunity than natural infection.