Jacobson v. Massachusetts
At first, exemptions for immunizations were only granted on a case-by-case basis if there were medical dangers connected with the vaccine and the patient.  However, more recently, more states are allowing religious and personal belief exemptions. Today, 48 states allow religious exemptions, while 18 states allow personal belief or philosophical exemptions.  Only two states, Mississippi and West Virginia do not allow any exemption other than a medical exemption. 
The issue in the immunization exemption cases revolves around specific statutory language allowing an exemption if a parent can prove a religious affiliation with a religious institution. In McCarthy v. Boozman and Boone v. Boozman, the Courts found that the section in question of the Arkansas Code violated the Establishment and Free Exercise Clauses of the First Amendment and the Equal Protection Clause of the Fourteenth Amendment.  Individuals affiliated with religion were given preferential treatment over those not affiliated with religion. As a result of the cases, the language in the Arkansas statute was amended to read: “the provisions of this section shall not apply if the parents or legal guardian of that child object thereto on the grounds that immunization conflicts with the religious or philosophical beliefs of the parent or guardian.” 
In 2010, there were 9,120 cases of whooping cough, with 10 reported deaths, in the state of California.  This was the highest number of whooping cough cases in the state since 1947.  After extensive study, researchers confirmed that the decision not to vaccinate children for nonmedical reasons has far-reaching effects, including raising the risk of infection for other children and their families.  The research showed that there tends to be clusters of people with nonmedical vaccine exemptions, which increases the potential for outbreaks. The census found that individuals within a high nonmedical exemption cluster in California were 2.5 times more likely to be in a whooping cough cluster than those in areas without high exemption rates.  The CDC reported an outbreak in 1985 when a 17-year-old immunization-exempt camper attended a Colorado camp and developed the measles.  Over 130 campers and counselors were unvaccinated and were exposed to the infected camper.  The staff and campers were from 24 different states and were placed under quarantine in their home states. A total of 50 associated cases occurred during this time.  This personal freedom versus public health issue creates complicated legal and ethical questions that must be explored before an outbreak of epidemic proportion occurs nationwide.
 Randall Neustaeder, The Vaccine Guide: Making an Informed Choice (2d ed. 1996).
 Jacobson v. Massachusetts, 197 U.S. 11, 25 (1905)
 M. Craig Smith, Case Note A Bad Reaction: A Look at the Arkansas Genera Assembly’s Reponse to Boozman v. Boozman, 58 Ark. L. Rev. 251, 252 (2005).
 Id. at 266.
 Vaccine Exemptions, John Hopkins Bloomberg School of Public Health (Oct. 2013), http://www.vaccinesafety.edu/cc-exem.htm.
 Smith, supra at 275.
 Id. at 258.
 Serena Gordon, Whooping Cough Outbreaks Tied to Shunning Vaccines. HealthDay (Sept. 30 2013), http://consumer.healthday.com/infectious-disease-information-21/misc-infections-news-411/whooping-cough-outbreaks-tied-to-parents-shunning-vaccines-study-680573.html.
 Measles in a Population with Religious Exemption to Vaccination—Colorado, Center for Disease Control & Prevention (Nov. 29, 1985), http://www.cdc.gov/mmwr/preview/mmwrhtml/00000644.htm.