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Frequently Asked Questions About Immunizations

Since the start of widespread vaccinations in the United States, the number of cases of formerly common childhood illnesses like diphtheria have declined dramatically. Immunizations have protected millions of kids from potentially deadly diseases and saved thousands of lives. In fact, certain diseases crop up so rarely now that parents sometimes ask if vaccines are even necessary anymore.

This is just one common misconception about immunizations. The truth is, most diseases that can be prevented by vaccines still exist in the world, even in the United States, although they occur rarely. The reality is that vaccinations still play a crucial role in keeping kids healthy.

Unfortunately, misinformation about vaccines could make some parents decide not to immunize their children, putting them and others at a greater risk for illness. To better understand the benefits and risks of vaccines, here are a few common questions.

What do immunizations do?

Vaccines work by preparing a child's body to fight illness. Each immunization contains either a dead or a weakened germ, or parts of it, that cause a particular disease.

The body practices fighting the disease by making antibodies that recognize specific parts of that germ. This permanent or longstanding response means that if someone is ever exposed to the actual disease, the antibodies are already in place and the body knows how to combat it and the person doesn't get sick. This is called immunity.

Will my child's immune system be weaker by relying on a vaccine?

No, the immune system makes antibodies against a germ, like the mumps-polio vaccination program has made it possible to replace the live virus vaccine with a killed virus form known as the inactivated polio vaccine (IPV). This change has completely eliminated the possibility of polio disease being caused by immunization in the United States.

Why should I have my child immunized if all the other kids in school are immunized?

It is true that a single child's chance of catching a disease is low if everyone else is immunized. Yet if one person thinks about skipping vaccines, chances are that others are thinking the same thing. And each child who isn't immunized gives these highly contagious diseases one more chance to spread.

This actually happened between 1989 and 1991 when an epidemic of measles broke out in the United States. Lapsing rates of immunization among preschoolers led to a sharp increase in the number of measles cases, deaths, and children with permanent brain damage. Similar outbreaks of encephalitis from tetanus, and pertussis vaccine that includes only specific parts of the pertussis cell instead of the entire killed cell. This vaccine, called DTaP, has been associated with even fewer side effects.

Do immunizations or thimerosal cause autism?

Numerous studies have found no link between vaccines and Rotavirus is one of the most common causes of diarrhea in young children. In 1999, a rotavirus vaccine was taken off the market because it was linked to an increased risk for intussusception, a type of bowel obstruction, in young infants. However, the U.S. Food and Drug Administration (FDA) recently approved a new, different rotavirus vaccine called RotaTeq, which was studied in more than 70,000 children and has not been found to have this increased risk. RotaTeq has been shown to prevent approximately 75% of cases of rotavirus infection and 98% of severe cases. The vaccine is now on the regular immunization schedule to be given orally to infants as a liquid during standard vaccination visits at ages 2 months, 4 months, and 6 months. Your doctor will have the most current information.

Do immunizations cause SIDS, multiple sclerosis, or other problems?

There are concerns, many of which circulate on the Internet, linking some vaccines to multiple sclerosis, sudden infant death syndrome (SIDS), and other problems. To date, several studies have failed to show any connection between immunizations and these conditions. The number of SIDS cases has actually fallen by more than 50% in recent years, whereas the number of vaccines administered yearly continues to rise.

Why does my child need to be immunized if the disease has been eliminated?

Diseases that are rare or nonexistent in the United States, like measles and polio, still exist in other parts of the world. Doctors continue to vaccinate against them because it's easy to come into contact with illnesses through travel. That includes anyone who may not be properly immunized who's coming into the United States, as well as Americans traveling overseas.

If immunization rates fell, a disease introduced by someone visiting from another country could cause serious damage in an unprotected population. In 1994, polio was brought to Canada from India, but it didn't spread because so many people had been immunized. It's only safe to stop vaccinations for a particular disease when that disease has been eradicated worldwide, as in the case of smallpox.

How long does immunity last after getting a vaccine?

A few vaccines, like the one for measles or the series for flu vaccine each year, if it isn't in short supply. Having been immunized last year won't protect someone from getting the flu this year because the protection wears off and flu viruses constantly change. That's why the vaccine is updated each year to include the most current strains of the virus.

The flu vaccine reduces the average person's chances of catching the flu by up to 80% during the season. But because the flu vaccine doesn't prevent infection by all of the viruses that can cause flu-like symptoms, getting the vaccine isn't a guarantee that someone won't get sick during the season. But even if someone who's gotten the shot gets the flu, symptoms will usually be fewer and milder.

Are vaccines continuously studied and improved because they're unsafe?

The FDA's Center for Biologics Evaluation and Research is the government agency responsible for regulating vaccines in the United States. Working in conjunction with the CDC and the NIH, they continuously research and monitor vaccine safety and effectiveness.

New vaccines are licensed only after thorough laboratory studies and clinical trials, and safety monitoring continues even after a vaccine has been approved. There have been — and will continue to be — improvements (such as those that have already been made to the DTaP and polio vaccines, for example) that will minimize potential side effects and ensure the best possible safety standards.

Where can I get affordable immunizations for my child?

Clearly, vaccines are one of the best tools we have to keep kids healthy, but the effectiveness of immunization programs depends on availability. You can receive inexpensive or free vaccines through many local public health clinics and community health centers, and campaigns to vaccinate kids often hold free vaccination days.

A program called Vaccines for Children covers Medicaid-eligible, uninsured, Alaskan and Native American populations, and some underinsured kids for routine immunizations up to 18 years of age. The vaccines are provided by the government and administered in the doctor's office. However, the doctor's visit itself is not covered (unless the child has insurance, including Medicaid). But some public health clinics may cover both the visit and the immunizations.

Where can I find out more about immunizations?

Read Larissa Hirsch, MD
Date reviewed: October 2007