A bill that would make it more difficult for parents to exempt their children from vaccines — legislation that has consumed the General Assembly during the final days of the session — died Thursday.

Democrats, who had sponsored the bill, delayed debate on it until Friday, effectively killing it.

“Everything we do up here has a cost. It costs you something to pass a bill. It costs you time, energy, resources,” Sen. Owen Hill, R-Colorado Springs, said after the bill died. “This shows it wasn’t worth the (Democrats’) time and energy. This wasn’t a big enough priority.”

House Bill 1312 looked like it might make it through before the end of session after it passed out of a Senate committee Wednesday night over the objections of Republicans and parents who showed up by the hundreds to testify in opposition. The committee limited testimony to two hours per side, angering opponents.

Hill credited those parents’ persistence with helping to stop the bill.

“It shows you can make a difference,” he said.

The bill would have required parents who want to exempt their children from vaccinations to go in person to a state health department office to fill out a form rather than simply giving the child’s school a note upon enrollment.

Health care officials from across the state advocated for the bill, saying the current national measles outbreak — with more than 700 cases reported in 22 states — made it all the more critical.

Gov. Jared Polis pushed back on the bill, however, saying last week he thought the in-person requirement might place an unfair burden on rural families. He also threatened to veto the first version of the vaccine bill that would have eliminated one or both of Colorado’s non-medical exemptions.

“The Governor appreciates Rep. Mullica and Senators Gonzales and Priola’s leadership in efforts to increase vaccination rates,” according to a statement from Polis’ office. “Improving the immunization rate is a top priority of our administration and through the Department of Public Health and Environment we will continue to identify best strategies and look forward to working with Rep Mullica, Senator Gonzalez, and Senator Priola and others to protect public health.”

Rep. Kyle Mullica, D-Northglenn, sponsored the bill, he said, in hopes of increasing Colorado’s kindergarten vaccination rate, which the Centers for Disease Control says is one of the lowest in the country.

He previously told The Denver Post he’d bring the bill back in 2020 if it failed to pass this session.

This is a developing story and will be updated.