If you’ve been following the effort at Colorado’s Capitol to make it more difficult for parents to opt their kids out of school immunization requirements, you’re likely aware that the state has some of the lowest vaccination rates in the nation.

But how low is low?

A Colorado Times Recorder records request to the Tri-County Health Department, which covers Douglas, Adams, and Arapahoe Counties, revealed that several schools in the area had MMR (measles, mumps, and rubella) vaccination rates that fall well below 50 percent for kindergartners during the 2018-2019 school year.

One school — Vega Collegiate Academy in Aurora — has a kindergarten MMR vaccination rate of just 23.8 percent.

Other schools with abysmal MMR vaccination rates include Assumption Catholic School in Denver, with a rate of 31.6 percent, and Our Lady Help of Christians Academy in Watkins, at 37.5 percent.

More than two dozen schools in the tri-county region didn’t submit vaccination records to the health department at all.

Amid the high number of measles cases across the U.S. last year, health experts warned that communities in the state where vaccination rates are lowest run the risk of experiencing an outbreak.

That, in addition to an executive order from Governor Jared Polis, prompted the health department to issue letters to schools in the area urging them to work on raising vaccination rates or report those rates in the state database if they hadn’t done so.

Health officials say that vaccination rates of 95 percent are required to achieve herd immunity, which protects those who can’t receive immunizations due to age or other medical reasons from contracting vaccine-preventable diseases.

The statewide MMR vaccination rate among kindergartners is 87.4 percent, well below the national average.

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A bipartisan bill advancing in Colorado’s General Assembly would tighten nonmedical vaccine exemptions in an attempt to raise vaccination rates in the state.

Current law requires proof of immunizations for school enrollment, but parents are able to easily opt-out for medical and religious reasons and personal beliefs by simply submitting a form to their school. The proposed legislation would require parents to either complete an online course designed by the Colorado Department of Public Health and Environment or obtain a signed form from a medical professional that provides immunizations.

A similar measure failed to advance last year in the final days of the legislative session, partially due to a lack of support from Polis. This version of the bill, however, has won the governor’s support, and as a result, proponents are more confident it will pass.

Still, the bill faces fierce opposition from vaccine opponents. The bill passed out of a Senate committee last week on a party-line vote following a hearing that saw over 14 hours of testimony, primarily from those who are opposed to a crackdown on immunization requirements.

The bill is scheduled for a vote in the full Senate tomorrow morning.

Correction: This article initially stated that Arma Dei Academy in Highlands Ranch had a kindergarten MMR vaccination rate of 17.9 percent. The school’s immunization data was incorrectly submitted to the health department. The school’s actual MMR vaccination rate is 82.1%.