NEW YORK (Reuters Health) - Many Web sites that oppose childhood vaccinations appeal to readers' emotions when trying to convey their message, and include claims about vaccination that are not supported by studies from peer-reviewed medical journals, according to researchers.

"The anti-vaccination sites...use heart-rending stories of children allegedly damaged or killed by vaccine reactions, often accompanied by pictures of these children," Dr. Robert M. Wolfe of Northwestern University in Chicago, Illinois, told Reuters Health.

"These sites are emotional because the driving force behind many of these Web sites is the rage of parents who are persuaded that their children were injured or killed by vaccine reactions," he added.

This emphasis on emotion can have a strong effect on the reader, Wolfe emphasized. "Each time parents are exposed to this information, a small number of persons may be influenced by what they read," he said.

Vaccinations have been accused of sparking a variety of illnesses, and some evidence suggests that vaccines may increase the risk of a child developing allergies or asthma.

However, the most common accusations leveled against vaccines--namely, that they cause sudden infant death syndrome (SIDS), autism or Crohn's disease--have not been validated by any scientific studies, Wolfe explained.

In order to evaluate how anti-vaccination Web sites present information, and what type of information they present, Wolfe and his team surveyed 22 Web sites that contained information that appeared to oppose vaccination.

The investigators found that all of the evaluated Web sites said that vaccines cause illnesses that appear to have no cause and arise spontaneously. Most sites also claimed that vaccines weaken a child's immune system. In addition, 95% of the Web sites said that side effects from vaccines are underreported, and another 64% contained information for parents about how they can avoid immunizing a child, such as by seeking a philosophical exemption.

In addition, Wolfe and his colleagues found that 55% of the Web sites included personal stories of parents who suspect that their child was hurt or killed as a result of vaccination, and another one quarter of the sites had pictures of the injured children.

Wolfe explained that claims of vaccine risks often are based on logic that identifies something as a cause of something else, simply because both events occurred during the same time period. "For example, autism often appears in early childhood around the same time vaccinations are given, so many parents blame the autism on the vaccines, especially MMR (measles, mumps and rubella)," Wolfe said.

"Several studies looked at this and found no relationship between MMR and autism," he added.

Wolfe and his team present their analyses of the anti-vaccination Web sites in the June 26th issue of The Journal of the American Medical Association.

Wolfe emphasized that despite his criticism of anti-vaccination Web sites, he is not opposed to the idea of debate. "I have no objection to anti-vaccinationists raising concerns over possible adverse reactions to vaccines, and their activism will almost certainly focus more attention on vaccines to help improve and maintain their safety. I only object to using sensationalism or misinformation," he said.

SOURCE: The Journal of the American Medical Association 2002;287:3245-

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