Vaccines are the most powerful tool to protect us against disease. Vaccines safeguard millions of children and adults from life-threatening illnesses. Vaccination is the administration of a purified fragment taken from bacteria or viruses. Vaccines "teach" the immune system to recognize and fight bacteria and viruses before an infected person can get sick. By giving a small "sample" of the germ, the body can develop resistance without actually getting the disease. Protection may need to be renewed periodically with "booster" vaccinations to boost immunity.
Smallpox was the first disease people tried to prevent by purposely vaccinating themselves. Smallpox is one of the most devastating diseases known to humanity. For centuries, repeated epidemics swept across continents, decimating populations and changing the course of history. Smallpox vaccination has been such a success that the disease has been eradicated worldwide.
As each new vaccine was introduced, the incidence of the targeted disease has dropped dramatically. Polio has been virtually eliminated from the Americas, and the number of measles and meningitis cases dropped sharply since the vaccines have been introduced. Vaccines and clean drinking water are the top public health achievements of the 20th century.