As Colorado lawmakers sat in a hearing room Sunday afternoon, listening to supporters of a bill to tighten vaccine exemptions, opponents outside the room — and outside the Capitol — got louder. They shouted, they stomped and they vowed not to leave.

Nearly 1,000 people gathered inside and outside the building to protest Senate Bill 163, as the ongoing demonstrations for racial justice, sparked by George Floyd’s killing, continued nearby.

A limited hearing for the bill that gave proponents and opponents 90 minutes each to testify ultimately passed on party lines with Colorado Democrats voting in favor, 7-4.

The bill requires those seeking nonmedical vaccine exemptions to either get an exception signed by a medical professional or to watch an online educational video about vaccines and get a certificate of completion. It also calls for improving data collection about exemptions in a central system with information to be distributed annually about each school’s vaccination rate.

Proponents say the bill is needed to improve Colorado’s low vaccination rates and curb the spread of preventable diseases. Opponents argue that it’s taking away parental rights and privacy.

“I understand this is a passionate topic on both sides of the issue, but the evidence is science-based,” said Rep. Kyle Mullica, a sponsor of the bill.

He added that Colorado isn’t even going as far as other states, some of which have completely removed nonmedical exemptions, and the bill reflects provisions because of opponent concerns.

“The status quo has gotten us to where we are today, which is last in the country (in immunization rates),” said Mullica, a Northglenn Democrat. “Something has to change.”

The mostly unmasked protesters rallying against the bill were joined by Robert Kennedy Jr., the son of the late Robert F. Kennedy, a Democrat. Kennedy spoke at the rally and told Colorado lawmakers in the House Health and Insurance Committee that they needed to put a stop to the bill.

“What they’re doing today is antithetical to every value the Democratic Party has expressed in over 200 years of history,” Kennedy said.

Although all of Colorado’s Republican lawmakers — except Sen. Kevin Priola, of Henderson, who is a bill sponsor — have opposed the bill, protesters also included groups of people who identified as Democrats.

Much of the divide was framed around science vs. deeply held beliefs, said Rep. Cathy Kipp, a Fort Collins Democrat. Kipp said she listened to every single proponent and opponent, but ultimately, her decision was clear.

“We have people with their beliefs trying to drown out facts, and it seems that this is where we are in the world today,” she said.

A majority of Coloradans support vaccinations and tightening exemptions, according to polling by Keating Research. The majority of medical professionals also back vaccines, with several testifying Sunday, including Dr. Sean O’Leary, who specializes in infectious disease at Children’s Hospital Colorado.

O’Leary said any information included in an education model would be based on science, not politics.

But opponents also brought their own medical professionals to testify against the bill — they said not enough information is provided about vaccine risks — as well as parents of children who they said were injured by vaccines and other anti-vaccine advocates.

Denver actor Theo Wilson said some of those in the anti-vaccine movement don’t want to be a part of it, but they woke up to a nightmare of finding out their kids were injured by vaccines. He said he never thought he would align with so many conservatives on an issue, but “my only allegiance is what’s going to help my community.”

Rep. Mark Baisley, R-Roxborough Park, decried any arguments about the science being clear.

“We heard powerful testimony today that challenges that scientific belief,” Baisely said.