Updated: July 23, 2012
School immunization laws were first established to control outbreaks of smallpox and have subsequently been used to avoid epidemics of vaccine-preventable contagious diseases, such as measles, whooping cough and polio.
Currently, all 50 states have school immunization laws—although there are differences in what may be required in different states.1
States require vaccines because they have a responsibility to protect both individuals and the entire population of their state.
Vaccine requirements for school entry help ensure that most people are protected through immunization. Because contagious diseases spread among susceptible people (those who have not been immunized and the small percentage of people for whom the vaccine was not fully effective), vaccination reduces the chance of infection and outbreaks of disease in schools and communities by reducing the number of unprotected people who may be infected and subsequently transmit the disease.
As of July 2012, all 50 states allow vaccination exemptions for medical reasons; 48 states allow exemptions for religious reasons; and 19 states allow exemptions for philosophical reasons.2
Medical exemptions are determined by a physician. These may occur when a child is allergic to some vaccine components or has an immune deficiency, such as occurs when being treated for cancer.
Religious exemptions are allowed when immunizations contradict the parent’s sincere religious beliefs.
Philosophical exemptions refer to other non-religious beliefs held by the parents who do not believe that their child should be immunized.
In most states, a child can attend school or day care if a proper exemption is obtained. However, when there is an outbreak of vaccine-preventable disease, children who have not had the disease and who have not been vaccinated are often excluded from school or day care until the risk of contracting the disease is over.
Mississippi and West Virginia are the only states that do not allow exemptions for religious reasons. The 19 states that allow exemptions for philosophical reasons are Arizona, Arkansas, Idaho, Louisiana, Maine, Michigan, Minnesota, Missouri, Nebraska, North Dakota, California, Colorado, Ohio, Oklahoma, Texas, Utah, Vermont, Washington, and Wisconsin.
There is no legal penalty for parents or guardians who obtain exemptions for philosophical or religious reasons; although in some states they could be found civilly liable if their child were to transmit a disease to another child.
Unvaccinated children are at greater risk of catching and spreading vaccine-preventable diseases.
Various studies have looked at the health consequences of exemptions from immunization laws. These studies have found that individuals claiming religious and/or philosophical exemptions from immunization (exemptors) are at a greater risk of contracting the diseases and thus put the rest of the population at risk by spreading infection, adversely affecting the health of the community.
One study, for example, found that on average, exemptors were 35 times more likely to contract measles than were vaccinated persons. The study also suggested that when more people are exempted from immunization the number of measles cases in the nonexempt population would increase—depending on how mixed both groups are.3
A similar study estimated that exemptors were 22.2 times more likely to acquire measles and 5.9 times more likely to acquire pertussis (whooping cough) than vaccinated children.4