Formerly eradicated measles outbreaks could be coming soon for Colorado kids

On Friday, Texas public health officials estimated that a measles outbreak had likely spread to between 200-300 people, across five counties in the western area of the state. Then, on Sunday night, word started coming out about three cases in Eastern New Mexico. Given measles is one of the most infectious diseases known to humankind, and that it takes 7-14 daysfor symptoms to become apparent, it’s possible that by next Sunday, more than a thousand people will be sick and the outbreak will have crossed more state boundaries.

That’s bad news for Colorado kids.

Colorado is at the bottom nationwide for kindergarten vaccination rates. Based on vaccination rates in 2022-2023, Colorado ranked 45^th out of the 50 states for rates of measles vaccination. (In 2019 the state had been dead last.) In 2024, vaccination rates ticked up slightly in Colorado but were still nothing near what they would need to be to provide herd immunity (the magic number where so many of a population are vaccinated that there is no chance for the virus to replicate in the population in order to reach the few that are not vaccinated).

Last year, 88 percent of kindergartners were vaccinated for measles in Colorado. Which means 12% or 7,036 kids did not have immunity. Measles is so highly infectious it is estimated that “90% of non-immune people exposed to an infective individual will contract the disease.”

Exposure to measles is fairly simple. It can float in the air between rooms and floors, it lasts on surfaces for hours after an infected person touches something, and it can be breathed or coughed directly from one person to another. The rate at which a disease can be transmitted is called its reproductive number. COVID’s ‘reproductive number’ was just over 3 according to the National Institutes of Health, which means every person who got COVID gave it to an average of 3 people. Measles reproductive number is estimated to be between 12-18 in a totallysusceptible population, but between 6.2 and 7.7 in a partially vaccinated population, which is what Colorado is.

Trying to estimate the impact of a disease outbreak in a specific population usually devolves into a game of calculator chess. Using peer-reviewed data multiplying the reproductive rates by the number of infected, health experts try to arrive at real numbers. It is always a guessing game.

The Colorado Department of Public Health and Environment refused to answer questions regarding the projected modeling of outbreaks or what was being done to prepare considering the neighboring states’ rapidly developing situations. They also declined to answer the estimated number of unvaccinated adult Coloradans.

We know that not all unimmunized kindergartners will be exposed to the measles virus. But if even a quarter of them are, then, according to the experts, 90% of that quarter will develop the virus and thus roughly 1,583 sick kids will infect (again roughly at an average reproductive rate of 6.9) 11,000 other Coloradans. Even if that’s where it stopped (and the 11,000 didn’t infect another 6.9 people, bringing the number to a mind-boggling 75,000) the consequences would be grave.

We know measles in most people is a mild to moderate illness with fever and characteristic rash. But the measles virus also hospitalizes around a fifth of its sufferers. One in 20 people who get measles ends up with pneumonia. And a very rare one in a thousand who come down with measles die of encephalitis. So again, playing statistical roulette, an outbreak that grew to 11,000 could be expected to hospitalize 2,200 people, give 550 pneumonia, and kill 11 people.

Colorado has 8,714 staffed hospital beds. On average, fewer than a third are available. A measles outbreak would come close to maxing those out. And that’s before you add in the rising number of flu cases Colorado is currently experiencing.

This hypothetical scenario doesn’t count the impact that measles can have on unvaccinated pregnant women including miscarriage, preterm delivery, and low birthweight. It also doesn’t count the 3% vaccination failure rate of the measles vaccine.  And it doesn’t count the roughly 5% of Colorado’s population who are between 57 and 63 years of age who received the “killed virus” version of the vaccination in its early years and have limited immunity.

Measles Was Once Declared Eradicated

The measles vaccination is 97% effective. The disease was actually declared eradicated in the U.S. in the year 2000. But in the decades since then, vaccines have become unpopular with some segments of the population. In 1998 a since defrocked UK physician published a study in the scientific journal The Lancet that claimed a connection between the MMR vaccine and autism. The study has been thoroughly refuted, but the damage was done. Social media, through so-called health influencers, including Robert F. Kennedy, Jr, who now leads the federal Department of Health and Human Services, has long held out in some sectors, that vaccines are more dangerous than the diseases they prevent. As a result, vaccination rates have slipped, and herd immunity ended.

In Colorado, this situation was made worse by one of the least restrictive vaccination laws in the country. All states allow for medical exemptions from measles vaccines – where vaccination would be medically dangerous for the recipient. In Mississippi, West Virginia, and California, medical exemption is the only exception allowed. All 47 other states allow for a religious belief exemption as well. But beyond that, a minority of states, including Colorado, allow for a parent’s “personal or philosophical belief” to be enough to waive the vaccination requirement. And Colorado’s statute makes the exemption easy, with an option where a parent can take an online ‘module’ in order to avoid having a health care provider sign the ‘opt out’ form. The module can be taken with the volume off and clicked through in less than 20 minutes. Some of the links are broken. But you can still get the opt-out form at the end of the exercise.

In 2019, following a measles outbreak in the Pacific Northwest, a Colorado legislator, then Rep. Kyle Mullica, who is now a state senator, introduced a bill to attempt to close the easy loophole in Colorado. But Gov. Jared Polis, also a Democrat, argued at the time that ‘forcing people to receive shots they don’t want creates a distrust of government.” The bill was dead on arrival. Mullica did not respond to a request for comment.

Before the measles vaccine became available in 1963, it is estimated that 3 to 4 million people in the U.S. were infected yearly. Of those, about 450 people died every year and another 48,000 were hospitalized. A thousand developed encephalitis.

Editor’s note: This story first appeared on the Colorado Times Recorder website.