Some parents are joining churches to qualify for special religious exemptions to avoid having their children vaccinated. Vaccination laws require that school-age children be immunized against childhood diseases such as mumps, measles and rubella, but a caveat in childhood immunization laws extends exemptions to parents who oppose mandatory vaccinations because of their religious beliefs. All but three states in the United States offer religious exemptions to vaccination, and 17 states offer "philosophical" exemptions. Sometimes, however, the confessions of faith that parents make are only to avoid vaccinating their children--a trend that health officials say raises the risk of epidemics Part of the problem, according to Daniel A. Salmon, a vaccination expert at the Johns Hopkins School of Public Health, is that national data do not make a distinction between exemption types. Salmon adds that the Internet and other tools further complicates things because they make it easy for people to look up Scripture verses to support their religious claims, even if they are not closely held.