The diseases prevented by the 12 childhood vaccines in the table below are bad ones. They can leave you blind, deaf, or paralyzed. They can cause painful infections of the lungs, skin, or bones. They can inflame the brain, turn healthy cells cancerous, or scar the heart. In some cases, they can kill.

Routine vaccination, however, has all but eliminated many of those diseases. For example, in 2005 there were only 66 reported cases of measles in the United States, 1 of polio, and none of diphtheria. In comparison, before vaccination became common some 500,000 people in the U.S. developed measles each year, 176,000 contracted diphtheria, and 16,000 came down with polio. Experts hope that new recommendations for the flu and meningitis vaccines, as well as entirely new vaccines against viruses that contribute to certain other common childhood diseases and even cervical cancer, will prove equally successful. And they caution that failure to vaccinate could lead to a resurgence of some previously controlled diseases. Indeed, recent outbreaks of the mumps and pertussis (whooping cough) may have stemmed in part from declining immunity due to inadequate vaccination. But there's little reason for the average person to avoid being vaccinated, because the potential benefit of vaccination greatly outweighs the potential risks. Those risks include minor reactions such as mild fever or pain at the injection site, severe but rare allergic reactions, and the vaccine-specific side effects listed in the table below.