States in the U.S. mandate immunization, or obtaining exemption, before children enroll in public school. Exemptions are typically for people who have compromised immune systems, allergies to the components used in vaccinations, or strongly held objections. All states but West Virginia and Mississippi allow religious exemptions, and twenty states allow parents to cite personal or philosophical objections. A widespread and growing number of parents falsely claim religious and philosophical beliefs to get vaccination exemptions, and an increasing number of disease outbreaks have come from communities where herd immunity was lost due to insufficient vaccination. More: en.wikipedia.org.