ATLANTA - Most people don't think about polio and diphtheria these days because those diseases have been stamped out in the United States, largely because of vaccines.

But a growing number of parents are seeking exemptions so their children don't have to get those vaccinations and others required by most states for kids to attend school.

Here's a rundown of the diseases the most commonly required vaccines help prevent:

• Polio, a paralyzing, sometimes deadly disease once seen in terrifying outbreaks, now only occurring in a few developing countries.

• Measles, a once-common illness that causes a rash and in rare cases can be fatal. In recent years, fewer than 100 cases were seen, but that number has at least doubled this year in the U.S.

• Mumps, a usually mild disease known for swelling the salivary glands, sometimes leading to more severe complications like deafness or miscarriage. Nearly 2,500 cases were reported last year.

• Rubella, or German measles, causes a rash but can trigger birth defects if acquired by a pregnant woman. Only a handful of cases are reported in the U.S. each year.

• Pertussis, or whooping cough, a highly contagious disease that can cause violent coughing in children. Nearly 20,000 cases were reported in 2010, an unusually bad year with several infant deaths.

• Tetanus, or lockjaw, can cause tightening of the muscles that prevents a victim from swallowing. Only a couple of dozen cases have been seen in the U.S. in recent years.

• Diphtheria, a bacterial illness that can lead to neck swelling and even death. Kids are at the greatest risk, but no confirmed case has been reported in the U.S. since 2003.

• Hepatitis B, a viral infection that attacks the liver and can lead to liver failure or death. About 2,700 cases were reported last year.