The state’s immunization reporting law would be gutted by a Republican-authored amendment unexpectedly added Thursday to a vaccination bill on the House floor.

House Speaker Dickie Lee Hullinghorst, D-Boulder, said there are procedural tools available to undo the vote, and Democrats are expected to attempt that Friday.

Thursday’s 33-32 roll-call vote to pass the amendment caught everyone in the chamber by surprise, given that the idea had been defeated previously on a voice vote. House staffers said some Democrats may have been confused about what they were voting on.

The amendment would allow parents to voluntarily include children’s vaccination information in the state’s immunization tracking system. Current law automatically puts that information in the system and allows parents to have it removed.

All children must be immunized to attend public schools, but state law allows parents to opt out for religious, medical or “personal objection” reasons.

The focus of Thursday’s debate, House Bill 16-1164, wouldn’t eliminate any of those exemptions, as prime sponsor Rep. Dan Pabon, D-Denver, kept pointing out.

The bill would require parents to file their exemption notices online with the Colorado Department of Public Health and Environment rather than submit paper forms to their local schools. Supporters argue the change will take a burden off school nurses and secretaries, provide more complete data to the department and be easy for parents.

Republican members repeatedly raised two big objections during debate, which stretched for more than 90 minutes: data privacy and the overall fate of exemptions.

“How can you guarantee this sensitive data will be protected” by the health department, asked Rep. Lois Landgraf, R-Colorado Springs.

Republicans fear the bill is a prelude to eliminating exemptions.

“There’s a fear that the next step is to require vaccinations,” said Rep. J. Paul Brown, R-Ignacio.

Others claimed data held by the health department wouldn’t be subject to federal student privacy law and that immunization reporting placed an unfair burden on college students.

Several GOP amendments were defeated. The parent-option amendment was adopted at the end of preliminary consideration, when members are allowed to offer amendments a second time and recorded votes are taken.

The exemptions bill has been contentious from the start. A House committee spent nearly seven hours on the issue last month before passing it 7-6.

How the bill might fare in the Senate is unclear.

Chalkbeat Colorado is a nonprofit news organization covering education issues. For more, visit co.chalkbeat.org.