What are vaccines?
“Vaccines help our bodies make protection against life-threatening infectious diseases,” says Anne Schuchat, MD, director of the CDC’s National Center for Immunization and Respiratory Diseases.
When a germ invades the body, the immune system recognizes it as a foreign invader. This sets off a cascade of events. The immune system makes antibodies, which are specialized molecules that stick to the invader and either inactivate it or mark it for destruction. Specialized immune cells also seek out and destroy germs and cells in which germs are multiplying. Other immune cells remember the germ so the next time a germ of the same kind tries to invade the body, the immune system will be able to mount an immediate response.
Vaccines offer a shortcut to immunity by raising protective immune responses before a germ invades. This gives the body a crucial head start that lets it prevent dangerous infections or make them less severe.