Background: In the United States, Western Europe and other areas, groups opposing universal childhood immunization are reported to be gaining political momentum.
Methods: A review was done of Internet sites opposing childhood immunization, with the goal of describing the philosophies and strategies used by the groups presenting them. A random sample of antivaccination Web sites was obtained using standard Internet search engines and the search terms "vaccination" and "immunization." These sites were analyzed for content, common themes, philosophy, affiliation with groups or organizations, and suggested strategies for avoiding vaccination.
Results: Twenty-six of the 51 sites found were randomly selected for review. Fifteen of these were associated with groups promoting the use of alternative medicine for preventing or treating infectious disease. Groups concerned with civil liberties were also represented, as were conspiracy theorists.
Conclusions: Many groups have an interest in opposing universal childhood immunization, and some of them have a prominent presence on the Internet. Physicians and parents should be aware of the existence of these groups and their philosophies. Further research and educational efforts to counter their effects is necessary.