Medical doctors say childhood vaccines are critically important but misinformation and myths abound when it comes to immunizations.

Thanks to many school-required vaccinations, certain diseases have become very rare, doctors said.

"There's definitely a need for vaccines," said Monika Pek, M.D., a pediatrician affiliated with Wayne Memorial Hospital. "It's always better to prevent a disease than to treat one."

Parents play a significant role in the long-term health of their children by making sure they are vaccinated, said Bruce A. MacLeod, M.D., president of the Pennsylvania Medical Society, in a news release.

MacLeod said parents used to be afraid that diseases such as measles, mumps, whooping cough, also know as pertussis, diphtheria and chicken pox would spread quickly in a classroom and school.

Now, thanks to immunizations, outbreaks of these diseases are not common in schools with high immunization rates, officials said.

Pennsylvania requires children to be vaccinated for eight diseases before starting school.

In addition, a few additional vaccinations are required before seventh grade.

According to the Pennsylvania Department of Health, students must receive vaccinations, before starting classes, for tetanus, diphtheria, polio, measles, mumps, rubella (German measles), hepatitis B and varicella.

There are common myths about vaccination shots, particularly that the measles/mumps/rubella (MMR) shots cause autism.

Pek said studies have disproven the notion that MMR causes autism.

Autism, the doctor said, occurs during development of the nervous system early in the womb, usually between 12 and 18 months.

Another myth is that multiple vaccines can overwhelm the immune system and spacing them out is safer, Pek said.

Vaccines today are much improved due to advances in science, said the pediatrician.

Children are undergoing more immunizations by age two but are receiving fewer antigens. An antigen is a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.

Pek said vaccines that are spaced out over time may leave children potentially susceptible to serious diseases.

"Through vaccination, children develop immunity without suffering the consequences of the serious diseases. Getting shots today can be considered a minuscule exposure compared to the tens of thousands of environmental antigens that infants successfully manage every day," Pek said.

Common afflictions for which children receive vaccinations include:

• Tetanus, also known as lockjaw, causes painful tightening of muscles throughout the body. Without treatment, tetanus is often fatal. The best solution is prevention through immunization, medical officials said.

• Diphtheria affects the back of the nose or throat by building a thick coating that makes it difficult to breathe or swallow. Vaccines protect individuals from sometimes deadly disease.

Children should get booster shots around age 11. Adults also need to have a booster shot every 10 years.

• Polio is a highly contagious viral infection that can lead to paralysis, breathing problems and possibly death.

“We cannot be complacent about polio. It is just a plane ride away,” said MacLeod, noting there has been a resurgence in the Middle East.

• Measles is a highly contagious virus that spreads through the air by breathing, coughing, or sneezing. It causes a rash all over the body as well as a fever, runny nose and cough. It can lead to ear infections, pneumonia, and encephalitis. The open sores from the rash can get infected with hard-to-treat bacteria. Measles can lead to brain damage and even death.

As with any vaccine, medical officials said, there can be minor reactions that could include pain and redness at the injection site. Headaches and fatigue may also occur.

Since the measles, mumps, rubella (MMR) vaccine is a live virus vaccine, there are medical reasons why some immune-suppressed people should not receive the vaccine.

Always check with your provider about MMR and all vaccines to make sure you get those recommended for your child, doctors said.

• The mumps virus is contagious and can be spread when a person coughs, sneezes, or talks. Touching contaminated surfaces can also help spread mumps. Complications from the disease may include viral meningitis and inflammation of testicles or ovaries.

Immunization for this disease can be achieved through the MMR (measles, mumps, and rubella) vaccine. Its safety record is excellent.

• Rubella is also known as “German measles” or “three-day measles.” Rubella is a virus that can be spread from an infected person by coughing or sneezing.

For the most part, rubella is mild, but there can be serious complications to the fetus if a pregnant woman contracts this disease.

The rubella vaccine is contained in MMR vaccine and can prevent this dangerous and sometimes deadly disease.

Side effects from rubella vaccine are usually mild – soreness around the injection site, fever, or rash.

• Hepatitis B can cause serious damage to the liver. If an infection becomes chronic, it can lead to liver failure, liver cancer, or cirrhosis.

There is no cure, but an effective vaccine series can help prevent hepatitis B. The hepatitis B vaccine series first became available in 1982.

According to the Center for Disease Control, no serious side effects have been reported since that time. Minor side effects may occur. Soreness at the injection site is the most common side effect.

• Varicella, better known as chickenpox, is a contagious disease caused by the varicella-zoster virus. It causes a blister-like rash, itching, tiredness and fever.

Chickenpox can be serious, especially in babies, adults and people with weakened immune systems.

Before the vaccine, about four million people would get chickenpox each year in the U.S.

The chickenpox vaccine is safe and effective at preventing the disease. Most people who get the vaccine will not get chickenpox. If a vaccinated person does get chickenpox, it is usually mild with fewer blisters and mild or no fever.