Illinois families who don't want their children to be vaccinated will have to get a doctor's note before claiming a religious exemption, but the new law won't affect students heading back to school in the coming weeks.

Gov. Bruce Rauner recently signed a bill aiming to reduce the number of unvaccinated children in the state's classrooms.

But because the law was passed after many children had already received their routine checkups or started school, the requirements won't go into effect until Oct. 16. That's the day after students must receive their vaccines or file objections.

Illinois is among 47 states that allow children an exemption from vaccines based on religious concerns.

The Illinois State Board of Education says there were more than 13,000 such exemptions in 2013.

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