What's the Story? Childhood Immunizations

The American Council on Science and Health (ACSH) Appreciates the Contributions of the Reviewers Named Below.

What Are Childhood Immunizations?

Childhood immunizations are a series of inoculations, or "shots," that protect children from dangerous infectious diseases. These shots work by priming the body's natural defenses to respond quickly and effectively to a particular disease-causing germ a virus or bacterium. Current recommendations call for all U.S. children to be immunized against 11 diseases: diphtheria, tetanus, pertussis (whooping cough), polio, measles, mumps, rubella (German measles), chickenpox (varicella), hepatitis B, Haemophilus influenzae type B (Hib) disease, and pneumococcal disease. Children in some western states should also be immunized against hepatitis A.

What Are the Benefits of Childhood Immunizations?

Immunizations have had a greater impact on reducing death and disability from infectious diseases than almost any other public health intervention. The rates of diphtheria, measles, mumps, pertussis, polio, rubella, tetanus, and invasive Hib disease have all been reduced by 97% or more by immunization.

What Are the Charges Leveled Against Immunizations?

Some people claim that childhood immunizations are no longer needed because the diseases that they prevent have become uncommon in the U.S. Concerns have also been raised about the possibility that some immunizations may increase the risk of sudden infant death syndrome (SIDS), autism, multiple sclerosis, diabetes, or other disorders. Recent changes in immunization recommendations (i.e., those pertaining to rotavirus vaccine and the use of the vaccine preservative thimerosal) have also prompted some people to question the safety of vaccines.

What Are the Facts?

Need for immunizations. Although most of the diseases that can be prevented by routine childhood immunization are now rare, immunization is still essential. The viruses and bacteria that cause these diseases still exist. If immunization rates are allowed to decrease, the diseases can come back.

Decreases in immunization rates have led to disease outbreaks in several industrialized countries in recent decades. During the late 1980s, measles vaccination rates decreased in the U.S. As a result, in 1989-91, a large outbreak of measles occurred, with over 43,000 cases and more than 100 deaths. The lowered rates of vaccine coverage were caused by parents abusing "philosophical" and religious exemptions from required vaccinations, due to unwarranted fears but the resulting epidemic sickened many immunized children as well. Levels of immunization against pertussis (whooping cough) dropped in both the United Kingdom and Japan during the 1970s. Within a few years, large outbreaks of pertussis occurred in both countries, with more than 100,000 cases and 36 deaths in the U.K. and more than 13,000 cases and 41 deaths in Japan.

Even diseases that have been under control for decades such as diphtheria or polio could return if immunization rates fell. Although these diseases are virtually unknown in North America, they still exist in other parts of the world, and they could be reintroduced into North America by travelers.

SIDS. There is no scientific evidence linking any type of vaccine with an increased risk of sudden infant death syndrome (SIDS). All of the available evidence indicates that reported cases in which an infant has died of SIDS shortly after receiving a vaccine are simply coincidences.

Infants are most likely to die of SIDS between the ages of 1 and 4 months. During this time period, practically all infants receive immunizations at least once. Thus, it is inevitable that a few infants will die of SIDS shortly after receiving immunizations. This is a matter of chance; it is not a cause-and-effect relationship.

Autism. Concerns have been raised about the possibility that the MMR (measles-mumps-rubella) vaccine may be linked to an increased risk of autism. (Autism is a developmental disorder characterized by impaired communication and social interaction, with repetitive activities that further restrict social interactions. It is estimated to occur in about two of every 1,000 children.) This issue was first raised in 1998, when British researchers published a study that seemed to show a link between the vaccine and autism. That initial study, however, was based on only 12 children. Subsequent studies of much larger groups of children have not confirmed an association, and no reputable scientists or physicians believe such a link exists.

MMR vaccine is usually given between the ages of 12 and 15 months. Symptoms of autism often become evident just a few months later, when parents or professionals notice that a child's language development is not proceeding normally. For this reason, it is likely that some children will be diagnosed with autism shortly after receiving MMR vaccine. There is no reason to believe, however, that the vaccine caused the disorder.

Multiple Sclerosis. Several reports in medical journals have described individual cases in which a patient developed symptoms of multiple sclerosis (MS) shortly after receiving immunizations. Individual case reports cannot distinguish between coincidences and cause-and-effect relationships, however. Studies of larger groups of people have not detected any association between immunization and the onset of MS.

Type 1 Diabetes. The cause of type 1 diabetes (the type that often begins in childhood) is not known. A variety of possible causal factors have been suggested, including immunizations. However, analyses of the relationship of immunizations to type 1 diabetes in humans have not found any causal link.

Rotavirus Vaccine. Rotavirus causes severe diarrhea in children and accounts for more than 500,000 physician visits and 50,000 hospitalizations in the U.S. each year. In August 1998, a vaccine against this virus became available, and doctors began to administer it to infants. Within the next few months, the U.S. government program that monitors vaccine safety received reports indicating that about 15 infants had developed intussusception shortly after receiving rotavirus vaccine. (Intussusception is a rare condition in which one segment of the intestine telescopes into another, sometimes leading to intestinal blockage.) Although the number of cases of intussusception was very small in comparison with the number of infants who had received the vaccine, analysis of the data suggested that the vaccine might indeed be associated with an increase in the risk of this rare problem. Therefore, the use of rotavirus vaccine was discontinued in October 1999 pending further study.

Thimerosal. Thimerosal is a mercury compound that has been included in some vaccines since the 1930s to help prevent bacterial contamination. There is no evidence that thimerosal has caused any health problems in children. However, because the overall exposure of children to mercury is a public health concern, efforts have been made, starting in 1999, to switch to vaccines that do not contain thimerosal preservative. All of the vaccines used for routine childhood immunizations are now available in preservative-free formulations.

The Bottom Line

Immunization is a safe and exceptionally effective component of preventive health care. Like all pharmaceutical products, vaccines can cause side effects. The most common side effects are minor ones: soreness at the injection site or low-grade fever. Serious side effects from immunizations are very rare. For all the vaccines in use today, the risk of serious side effects associated with receiving the vaccine is far lower than the risk associated with not receiving the vaccine and thereby remaining susceptible to the disease that it prevents.

All new vaccines must undergo extensive scientific testing before they can be approved for use in the U.S. Once in use, vaccines are continually monitored for safety.

Frightening stories about possible risks of vaccines sometimes appear in the news media and on the Internet. Parents who see these reports may believe that their children would be better off not having their shots. However, this is not true. Children are far more likely to stay healthy if they receive their immunizations than if they do not. Parents who have any concerns about their children's immunizations should discuss them with the child's health care provider.