The First Amendment guarantees Freedom and Free Exercise of Religion. Government accommodation of religious practice has long been recognized as essential to religious liberty in the United States. If state statutes or policies become a millstone for religious practice, the government may establish narrowly construed exemptions or accommodations for those religious beliefs.
The arguments for religious freedom and free exercise thereof have been successfully used in fights for religious exemption to compulsory vaccination for adults and minors alike.
Compelling vaccinations in order to protect public health does not impinge on a citizen's constitutional right to free exercise of religion. However, exemptions are intended for people who hold sincere religious or spiritual beliefs opposing vaccination. Therefore, if the state enforced a vaccination policy and mandated an immunization practice, it would be an infringement on that citizen's right to exercise his beliefs.
"The powers not delegated to the United States by the Constitution, nor prohibited by it to the states, are reserved to the states respectively, or to the people."
The police power of the states as guaranteed is plenary in function. The power belongs to the state legislature and allows such laws to be enacted that affect public security, welfare, health, justice and morality. Therefore, as argued under Jacobson v. Massachusetts, the state has a constitutionally granted power to enact mandatory vaccination laws for the security and welfare of its citizens.
"No state shall...deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws."
The Fourteenth Amendment arguments regarding substantive due process rights have been used to raise issues of liberty interest in relation to compulsory vaccination mandates. The question is often regarding the guarantee of that protects United States residents against arbitrary legislative actions.