Opposition due to the safety of the vaccine has been addressed through studies, leaving opposition focused on the sexual implications of the vaccine to remain. Conservative groups in the U.S. have opposed the concept of making HPV vaccination mandatory for pre-adolescent girls, asserting that making the vaccine mandatory is a violation of parental rights. They also say that it will give a false sense of immunity to sexually transmitted disease, leading to early sexual activity. (See Peltzman effect) Both the Family Research Council and the group Focus on the Family support widespread (universal) availability of HPV vaccines but oppose mandatory HPV vaccinations for entry to public school. Parents also express confusion over recent mandates for entry to public school pointing out that HPV is transmitted through sexual contact, not through attending school with other children.