The new rules, effective July 2016, will require parents seeking non-medical exemptions from school and child-care vaccine requirements to submit them more than once. They will be required at each age when recommended vaccines are due for pre-kindergartners and annually from kindergarten through 12th grade.
Currently, the state requires submission of an exemption request just once.
Gov. John Hickenlooper said in a written statement that the new rules will strengthen immunization rates in the state, which are among the lowest in the nation.