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Vaccines and Autism

CDC: Vaccines and Autism
Facts About Autism
Autism Fact Sheet
What is Autism?
MMR Vaccine and Autism
CDC�s Autism Research Efforts
Inflammatory Bowel Disease (IBD) and Vaccines
References and Other Resources

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Rotavirus Vaccine

CDC recommends that healthcare providers and parents postpone use of the rotavirus vaccine for infants, at least until November 1999, based on early surveillance reports of intussusception (a type of bowel obstruction that occurs when the bowel fold in on itself) among some infants who received rotavirus vaccine.

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Thimerosal in Vaccines

Thimerosal-Containing Vaccines and Neurodevelopmental Disorders. Report by the Institute of Medicine's Immunization Safety Review:

Historical Information:

Other Resources:

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The safety record on vaccines

Vaccines are very safe. Today, the United States has the safest, most effective vaccine supply in history. Vaccines have provided Americans with tremendous health benefits, with a minimum of risk. In 1996, almost 81.6 million immunizations were given in the U.S. alone, and many billions more have been given safely around the world.

The prosperity of any nation is directly linked to the health of its population. The widespread availability and acceptance of immunization in America has prevented a huge burden of disease, complications, and deaths from polio, measles, pertussis (whooping cough), tetanus (lockjaw), diphtheria, mumps, and rubella ("German" measles). As recently as 1990, Haemophilus influenza type b was a common, devastating illness and the leading cause of bacterial meningitis in U.S. children. Now, most pediatricians (doctors who specialize in diseases of childhood) just finishing their training have never seen a case, thanks to immunizations.

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Vaccine risks

As with any medical procedure or medication, immunizations are associated with a risk of an adverse reaction. Typical reactions may include warmth, redness, and tenderness at the site of the injection, and irritability. Potential serious reactions vary according to the type of immunization, and include the potential for seizures, damage to the brain or central nervous system, and death. However, most reactions are minor and treatable. There are so few deaths that could plausibly be connected to vaccine, and the risk is so small, that it is hard to assess statistically.(1)

The National Vaccine Program Office supports continuous vigilance, so that any increase in risk from a vaccine is quickly recognized and so that measures can be taken to make vaccines even safer. The CDC National Immunization Program and the Food and Drug Administration (FDA) have systems in place for monitoring reports of reactions. Among these is the Vaccine Adverse Event Reporting System (VAERS) , which is described more fully below in the section titled "How Vaccine Safety Is Monitored."

Vaccines have been so successful in preventing disease in the U.S. that in recent years, the annual number of reports to VAERS have exceeded the total number of reports of routine childhood vaccine-preventable disease. This may lead some people to believe that the vaccines are dangerous. However, based on the very large numbers of data collected nationwide through the various data systems, the risk of a serious adverse reaction to an immunization is extremely small. The risk of the disease itself is substantially more serious than the risk of the immunization. The risks of specific vaccines are posted on the CDC National Immunization Program home page, which you can access by clicking here.

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How vaccine safety is tested

The U.S. government agency charged with assuring the safety of vaccines in development, vaccines in clinical trials (experimental studies that occur in phases, gradually increasing the number of people involved in testing), and vaccines in use is the FDA.

In general, all vaccines must receive two licenses before being released for marketing: one for the vaccine, and one for the manufacturing plant. It is the FDA that defines the rigorous studies and many documents required to get the license, as well as actually granting or refusing a license. The FDA is also involved in the type of labeling that is done and the information that is given to health care professionals about how to use the vaccine, precautions, known side effects, and other aspects of the vaccine. Once a license is granted, manufacturers may begin producing the vaccine, but they must continuously test each lot of the product for potency, safety, and quality, and the results of these tests must be given to the FDA.

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How vaccine safety is monitored

Once a vaccine is in use, physicians must keep very careful records of who receives the vaccine and what lot of vaccine was used. This way, if a problem arises, it is possible to track down the lot that was used, so it can be tested and evaluated to see if the vaccine was at fault.

Administering the vaccine is not the end of the monitoring process. As described by the Institute of Medicine in a 1997 workshop summary,(2)adverse events that may be linked with vaccines are monitored in four ways:

1.The Vaccine Adverse Event Reporting System (VAERS). The National Childhood Injury Act was established in 1986. This law requires health care providers to report any serious adverse events that occur within 30 days after vaccination with any vaccine. The reports must be submitted to VAERS, which was set up in 1990 and is managed by the Centers for Disease Control and Prevention and the FDA. The VAERS system is capable of creating clues that may be useful in uncovering potential new adverse events and any change (increase or decrease) in the rate of reporting of previously known adverse events associated with vaccines. However, it is a "passive" system of gathering data, and therefore may not capture as many events as an aggressive system would. More important, since lot sizes vary and the number of doses within a lot that have actually been given is not known, the raw number of reported adverse events, by itself, does not make it possible to interpret whether there is an actual problem. For example, "three adverse events" may have entirely different meaning if a million doses have been given, versus 30 doses. For additional in-depth information on VAERS, click here.
Patients, parents, or even non-relatives who witnessed or who are aware of a reaction can also submit a report to VAERS. A copy of the VAERS reporting form and instructions for how to submit it can be obtained by calling 1-800-822-7967. You can also download and print a copy of the form from the web site of the FDA. To access that form, click here

2. The Vaccine Safety Datalink (VSD). The VSD was established by the CDC in 1990. It links large databases of four health maintenance organizations containing data on a known population size (more than 500,000 children of ages 0 to 6 years, both vaccinated and not vaccinated), in Oregon, Washington, and California. Because this system actively finds cases and systematically reviews medical records from a population of known size, the VSD captures more complete data on adverse events associated with vaccination. The VSD makes it possible to do large epidemiologic studies of vaccine adverse events, captures information on less commonly occurring types of adverse events, and helps determine whether an event is linked with a vaccine or with some other cause.

3. Surveillance by vaccine manufacturers. Manufacturers are required by the National Childhood Vaccine Injury Act of 1986 to report adverse events to the Department of Health and Human Services. (3)

4. Monitoring by the FDA. The FDA monitors adverse events reporting rates, using both the VAERS data and manufacturers� data. Among the things FDA looks for are large numbers of adverse event reports early in the circulation of a lot, clusters of similar cases, syndromes (groups of symptoms), or other patterns; additional information from other sources with knowledge of a particular case; patterns of reported adverse events linked to final lots filled from the same bulk vaccine; and documentation that lots in question have passed all the required tests.

The VSD and VAERS are complementary methods of monitoring data. VAERS is a signal generator, designed to provide clues that there may be problems with specific lots of vaccine that require more investigation. VSD provides actual incidence rate of diseases and events that occur around the time of vaccination and at times not linked to vaccination, making it possible to evaluate whether the vaccine actually caused the adverse event and, if so, the magnitude of the problem.

Information about the concept of a national vaccination registry will be posted on this site in the future.

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Parents have a role in vaccine safety, too

Government agencies and vaccine manufacturers have strict guidelines for vaccine safety, but a parent plays a role, too. Here are several things a parent can do:

1.If any aspect of your child�s appearance or behavior gives you concern after a vaccination, report it to your child�s health care provider immediately. Respond to your instincts as a parent. If you feel the situation is an emergency, say so. Write down what happened and the date and time it happened. Ask your health care provider to file a Vaccine Adverse Event Report form or call 1-800-338-2382.

2.Learn the facts about immunizations and infectious diseases. In 1993, a Gallup poll of 1,000 parents of children under five years of age showed a great gap in many parents� understanding of immunization and infectious diseases: 47% were unaware that polio is contagious, 36% didn�t know that measles can be fatal, and 44% didn�t know that Haemophilus influenzae type b was the leading cause of potentially fatal bacterial meningitis, a disease that as recently as 1985 was a major killer of infants and toddlers. The section on Immunization Concepts and the Quick Definitions of Immunization Terms in this site provide a quick, basic course on immunization. The Ten Tips on Evaluating Information on Immunization, which follows this section, can help you sort through information from various sources. The CDC National Immunization Program web site has a wealth of information, including information by specific immunizations. Click here to go to the Question and Answer section of that site.

3.Periodically review the Current Vaccines and Recommended Vaccination Schedule, which is posted in the "What�s New?" section of the CDC National Immunization Program�s web site. Vaccination schedules are available for adults or children. By following the schedule, you can be sure to get your child�s immunizations at the safest and most advantageous age.

4.Always keep a record of your child�s immunizations, and bring it with you to office visits. This will ensure that vaccines are given on schedule and that your child does not receive excess immunizations. This is especially important if you move, change doctors, or vaccinations are given anywhere other than in your regular physician�s office (for example, if your child is given a tetanus [lockjaw] shot during an emergency room visit).

5. Review the Standards for Pediatric Immunization Practice, which provides guidelines on what your pediatrician or family health care provider should know and do about vaccines.

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In the rare event that something goes wrong: The National Vaccine Injury Compensation Program (VICP)

The National Childhood Vaccine Injury Act of 1986 established the VICP. This program went into effect in October 1988 and is a Federal "no-fault" system designed to compensate those individuals, or families of individuals, who have been injured by childhood vaccines, whether administered in the public or private sector. The act covers the following vaccines: diphtheria, tetanus, pertussis (DTP, DTaP, DT, TT, or Td), measles, mumps, rubella (MMR or any components), polio (OPV or IPV), Haemophilus influenzae type b (Hib), rotavirus (RV), hepatitis A (HAV), hepatitis B (HBV), meningococcal (MCV4 or MPSV4), pneumococcal conjugate (PCV7), human papillomavirus (HPV), influenza (TIV or LAIV) and varicella (chicken pox) (VZV). While the act was written with vaccine-injured children in mind, it also applies to any adult who is injured by the vaccines listed above. Complete information on this program is available at the Health Resources and Services Administration website:

*For additional information on vaccine safety, go to the Questions and Answers section of this site

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1. Centers for Disease Control and Prevention. What you may have heard about vaccines...and what you should know [fact sheet]. Atlanta: CDC, Office of Communications, 1997:1.

2. Institute of Medicine, Vaccine Safety Forum, Board on Health Promotion and Disease Prevention. Vaccine Safety Forum: Summaries of Two Workshops. Washington DC: National Academy Press, 1997.

3. Food and Drug Administration, Center for Biologics Evaluation and Research. Vaccine adverse event reporting system [online]. Washington, DC: FDA, 1997. Available at

Last revised: April 23, 2007


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