A bill to more accurately track vaccination rates is moving forward in the state legislature, but faces an uphill climb to win final passage.

The bill would centralize data about immunizations with the state health department, rather than school districts. It passed on a party line vote in a Democratically-controlled House committee. It now moves to the full House, where chances of passage are good.

But it then needs to win approval in the Senate, which is controlled by Republicans, many who oppose the bill on privacy grounds.

About a quarter of preschool age children in Colorado don’t receive all recommended doses of six key vaccines, according to the state’s 2016 Health Report Card, by the Colorado Health Foundation, which found the state ranked 25th in U.S. in that category.