For more than 40 years, Mississippi had one of the strictest school vaccination requirements in the nation, and its high childhood immunization rates have been a source of pride. But in July, the state began excusing children from vaccination if their parents cited religious objections after a federal judge sided with a “medical freedom” group.

Mississippi is not an isolated case. Buoyed by their success at overturning coronavirus mandates, medical and religious freedom groups are taking aim at a new target: childhood school vaccine mandates, long considered the foundation of the nation’s defense against infectious disease.

Until the Mississippi ruling, the state was one of only six that refused to excuse students from vaccination for religious or philosophical reasons. Similar legal challenges have been filed in the five remaining states: California, Connecticut, Maine, New York and West Virginia. The ultimate goal, according to advocates behind the lawsuits, is to undo vaccine mandates entirely, by getting the issue before a Supreme Court that is increasingly sympathetic to religious freedom arguments.