Adults aren’t required to get vaccinated — but all states require children to get vaccinated to attend school, although they grant different levels of exemptions.
Nineteen states allow medical, religious, and philosophical exemptions. Twenty-eight states and the District of Columbia allow medical and religious exemptions. California, West Virginia, and Mississippi only allow medical exemptions.
There’s no clear connection among the states that allow philosophical exemptions. Oregon and Texas, often on opposite ends of the political spectrum, both have fairly permissive policies.
States’ exemption policies pose a potential danger to public health, because letting people skip vaccines makes it more difficult to reach herd immunity, when enough people are vaccinated that a pathogen can’t find new human hosts to which to spread.