Vaccination Requirements and Exemptions

Vaccination is one of a small group of medical interventions with direct benefits to both individuals and communities. When a large percentage of a population is vaccinated against a pathogen, the entire community--both those vaccinated and unvaccinated--receive additional protection. This concept, known as 'herd immunity,' is a primary justification for mandatory vaccination policies in the United States.

In the U.S., all states require children attending public school or state-licensed day care facilities to receive a series of vaccinations. Specific requirements vary from state to state. (Some states specifically include private schools in these requirements, while most private schools voluntarily adopt similar, if not identical, requirements for their students.) The term "mandate" is somewhat misleading when applied to vaccination, however. The last time the U.S. required vaccination without exception--a true mandate--was during World War I.1 Today, all states except Mississippi and West Virginia have procedures which allow parents to exempt their children from state vaccination requirements on the basis of religious and/or personal beliefs.

Vaccination requirements for school and day care attendance are seen as critical to ensuring high rates of vaccination in the U.S. Public health officials cite a number of reasons for this belief. Linking vaccination with school attendance, itself required by law, ensures that vaccines reach the greatest number of children. Schools are a prime venue for the transmission of vaccine-preventable disease, and active school-age children can further spread disease to their families and others with whom they interact.

An additional benefit of vaccination requirements is its ability to address disparities in vaccination rates. In a 2008 study published in Pediatrics, a hepatitis B vaccination requirement was found to improve large racial and ethnic disparities in vaccination rates seen prior to the introduction of the mandate.2

While school vaccination requirements have contributed to significant decreases in the incidence of many vaccine-preventable diseases, opposition to these policies is increasingly prevalent. Such resistance is neither new nor unique to the United States, however. In fact, the term "conscientious objector" originally referred to opponents of England's aggressively-enforced smallpox vaccination requirement in the late nineteenth century.3

Establishing a vaccine school-entry requirement and state laws on exemptions

State governments are solely responsible for school vaccination requirements. The federal government has no role in recommending, approving, or enforcing policies that mandate vaccination for school or day-care attendance. Through the Department of Health and Human Services and its agencies--particularly the Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC)--the federal government licenses new vaccines for use in the U.S., provides recommendations on populations for whom specific vaccines should be administered, finances vaccines for uninsured or underinsured children, monitors vaccine safety, and promotes vaccination nationwide.4 However, the decision to add a vaccine to a state's required vaccination schedule is made only by state public health officials or state legislatures.5 In some states, adding a vaccine requirement can occur through regulations issued by its health department; others require a bill to be passed by the legislature and signed by the governor.

As noted previously, all 50 U.S. states and Washington, DC have school-entry requirements for vaccines. 48 allow exemptions for religious reasons (West Virginia and Mississippi are the only exceptions) and 21 allow for philosophical (also known as personal-belief) exemptions.6,7 All states also permit exemptions for medical reasons, such as children with weakened immune systems or allergic to a vaccine component. Home-schooled general are generally not subject to state vaccination requirements, making this option attractive to parents who wish neither to vaccinate their children nor to seek an exemption. As of 2010, only North Carolina requires vaccination of home-schooled children.8

Children who have not received all required vaccinations or a valid exemption are not permitted to attend school, although enforcement varies widely among states. In the event of an outbreak, children with exemptions can be excluded from school attendance.

Religious and philosophical exemptions

The distinction between a philosophical (personal-belief) and a religious exemption is often ambiguous. The precise language varies from state to state, but for religious exemptions, states have required religious objections to be based on tenets of a specific, organized religion. Laws phrased in this way have been successfully challenged as violating Constitutional protections regarding the free exercise of religion, however. As a result, many states speak in far more general terms, such as "a sincere and meaningful belief... held with the strength of traditional religious convictions."10

Parents who refuse vaccination on philosophical grounds point not to religious beliefs but often cite their right to determine the medical care of their children without government involvement. However, the U.S. Supreme Court has ruled on several occasions that state vaccination requirements are permissible, writing that "the very concept of ordered liberty precludes allowing every person to make his own standards on matters of conduct in which the society as a whole has important interests."11

Exemptions and herd immunity

An individual's decision to refuse vaccination can have societal consequences. In a community where vaccination rates are very high, the likelihood of members being exposed to a pathogen is quite low. As a result, it may actually be in any one individual's best interest not to get vaccinated, since they already benefit from a reduced likelihood of infection (due to high vaccination rates) without exposing themselves to any vaccine-associated risks, however small. An individual refusing vaccination by this logic could be termed a "free rider." However, if too many individuals adopt this approach, the additional benefits of herd immunity will be lost, and, since no vaccine is 100% effective, even those vaccinated will be at an increased risk.12 Recent outbreaks of vaccine-preventable diseases among the unvaccinated suggest that relying solely on herd immunity for personal protection is a dubious strategy, at best.

The impact of exemptions

From 1991 to 2004, the average rate of non-medical exemptions from immunization requirements increased from .98 to 1.48%.1 Similar increases in non-medical exemptions have been observed during the past several years. This rate varies widely among states and even within particular regions thereof. Rates are especially high in states with personal-belief exemptions and those with particularly easy processes to obtain an exemption.

Two studies published in the Journal of the American Medical Association found that children exempt from vaccination requirements were more than 35 times more likely to contract measles and nearly 6 times more likely to contract pertussis, compared to vaccinated children.13, 14 This research also showed that communities with lower rates of immunization had higher rates of infection among vaccinated children than those with higher vaccination rates. Similar correlations between exemption rates and incidence of vaccine-preventable disease has been found in both the United Kingdom and Japan.15

-- By Ben Kleifgen, Temple University School of Medicine ( and Justin Silpe, University of Michigan (; Updated July 2010.

1 Omer, SB, Pan WK, Halsey NA, et al. Nonmedical Exemptions to School Immunization Requirements: Secular Trends and Association of State Policies with Pertussis Incidence. JAMA 2006;296:1757-1763.
2 Morita JY, Ramirez E, Trick WE. Effect of a School-Entry Vaccination Requirement on Racial and Ethnic Disparities in Hepatitis B Immunization Coverage Levels among Public School Students. Pediatrics 2007;121(3):e547-e552.
3 Durbach, N. Class, Gender, and the Conscientious Objector to Vaccination, 1898-1907. The Journal of British Studies 2002;41(1):58-83.
4 Malone KM, Hinman AR. Vaccination Mandates: The Public Health Imperative and Individual Rights. In: Goodman RA, Rothstein MA, Hoffman RE, et al., eds. Law in Public Health Practice. New York: Oxford University Press, 2003: 262-84
5 National Network for Immunization Information:
6 Vaccine Exemptions. Johns Hopkins Bloomberg School of Public Health - Institute for Vaccine Safety, 2008. (Accessed June 14, 2010, at
7 The 21 states that allow exemptions for philosophical reasons in school and daycare are: Arkansas, Arizona, California, Colorado, Idaho, Louisiana, Maine, Michigan, Minnesota, New Mexico, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Utah, Vermont, Washington, and Wisconsin.
8 Khalili D, Caplan AL. Off the Grid: Vaccinations among Home-Schooled Children. Journal of Law, Medicine, and Ethics 2007;35(3): 471-477.
9 Schwartz JL. Unintended Consequences: The Primacy of Public Trust in Vaccination. Michigan Law Review 2009;107:100-104.
10 Malone KM, Hinman AR. Vaccination Mandates: The Public Health Imperative and Individual Rights. In: Goodman RA, Rothstein MA, Hoffman RE, et al., eds. Law in Public Health Practice. New York: Oxford University Press, 2003: 262-284
11 Ibid.
12 Plotkin SA, Orenstein WA, and Offit PA, eds. 2008. Vaccines, 5th ed. Elsevier Inc., Philadelphia, PA.
13 Feikin DR, Lezotte DC, Hamman RF, Salmon DA, Chen RT, and Hoffman RE. Individual and Community Risks of Measles and Pertussis Associated With Personal Exemptions to Immunization. JAMA 2007;284:3145-3150.
14 Salmon DA, Haber M, Gangarosa EJ, Phillips L, Smith NJ, and Chen RT. Health Consequences of Religious and Philosophical Exemptions from Immunization Laws: Individual and Societal Risk of Measles. JAMA 1999;282:47.
15 Plotkin SA, Orenstein WA, and Offit PA, eds. 2008. Vaccines, 5th ed. Elsevier Inc., Philadelphia, PA.

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