15 Things You Need to Know About Vaccines

Experts answer common questions about vaccines for children and adults.

Photo by Bloomberg/Getty Images

How Do Vaccines Work?

When you get sick, your body creates special proteins called antibodies to fight the infection. The next time you are exposed to that same virus or bacteria, those antibodies keep you from getting sick again. Vaccines do the same thing without making you ill. “Vaccines induce the protective immunity that is a consequence of natural infection, without having to pay the price of [becoming sick with] a natural infection,” says Paul Offit, chief of the division of infectious diseases and the director of the Vaccine Education Center at the Children’s Hospital of Philadelphia. Scientists create vaccines by disabling a virus or bacteria so that it is not able to cause disease but still can prod your body to make antibodies to it. Those antibodies will bind to infections in the future and keep them from making you sick. Getting a vaccine is “like having a protective bubble that keeps viruses and bacteria from attacking your body,” says Offit.

Have Vaccines Eradicated Common Diseases?

“Vaccines are one of the 10 greatest public health achievements of all time, but not all diseases are completely gone, and that’s why it remains critical for parents to vaccinate their children and themselves,” says Melissa Stockwell, assistant professor of pediatrics and population and family health at Columbia University in Manhattan. The only disease that vaccines have successfully eradicated (meaning it will never reoccur) is smallpox. There are others that might be eradicated if vaccination rates become high enough, including polio, measles, rubella (German measles), and chicken pox (varicella). Of those, the only disease close to eradication is polio. For other diseases, such as tetanus, eradication is not possible, because the bacterium that causes it lives in the soil and can never be eliminated.

But vaccines have “dramatically reduced the amount of suffering and hospitalization or death caused by disease,” says Offit. “For diseases like rotaviruses, influenza, chicken pox, and whooping cough, vaccines have turned them into diseases that are mild or without symptoms.” Before there was a vaccine for it, there were 8,000 deaths a year in the United States from whooping cough (also known as pertussis); now there are around 50. Before a vaccine was invented for measles, there were 4 million cases in the U.S. and between 500 and 1,000 deaths annually; in 2011, there were 122 cases and no deaths. Polio used to kill 1,500 people a year; now polio is no longer a concern in the United States.

How Long Do Vaccines Last?

Some vaccines, such as the measles, mumps, and rubella (MMR) vaccine and poliovirus vaccines, offer lifelong protection. Others, including influenza and meningococcal vaccines, as well as vaccines containing pertussis, diphtheria, and tetanus, require boosters in the teen and adult years.