Mandatory immunization requirements protect both the individual and the community against the morbidity and mortality associated with vaccine-preventable illnesses. Despite the overwhelming evidence of safety and societal benefit, vaccines are associated with a small degree of risk to the individual of untoward reactions even when the vaccine is properly manufactured, handled, and administered. Some people who are unaware or misinformed regarding the risk-benefit ratio of vaccines, who do not believe the science of clinical trials and other study designs, or who hold personal beliefs inconsistent with vaccination may have a different opinion regarding the balance of individual rights and community benefit. Mandatory immunization laws may result in restrictions on individual or parental rights (such as excluding some unvaccinated children from school), although justification of state laws requiring immunizations have been upheld by numerous courts throughout the country, including the US Supreme Court. The basis of this restriction of individual rights is that failure to vaccinate affects the safety of others and does not fulfill the obligation of society to ensure that children receive optimal preventive health care.