Colorado’s school vaccination rate holds steady below “herd” immunity

Colorado’s vaccination rate held steady in the most recent school year, but pockets of the state remain vulnerable to outbreaks of measles and other diseases.

Last school year, 92.1% of children from kindergarten to 12th grade had all of their required shots or a valid exemption, which was virtually unchanged from the 2022-2023 school year. Kindergarteners had lower compliance rates, with 90.1% either up to date on their shots or holding an exemption.

About 93.6% of all schoolchildren had their combined measles, mumps and rubella shots, which are among the most important because a person with measles can infect nine out of 10 unvaccinated people they come across, said Susan Lontine, executive director of Immunize Colorado. Only 88% of kindergarteners had been vaccinated against measles, though.

“It’s still nowhere near the 95% we need for (population-level) protection,” she said.

While people develop individual immunity after getting vaccinated, “herd immunity” makes sure diseases can’t spread through the population, protecting those who can’t get vaccinated because of medical conditions and babies too young to receive their shots.

In nine school districts, mostly in rural areas, fewer than  80% of kids have their measles, mumps and rubella shots, making them extremely vulnerable to outbreaks, Lontine said.

During the 2019-2020 school year, 95% of K-12 students had either their shots or an exemption. That dropped slightly during the 2020-2021 school year, and more significantly the following year. No one knows how much of that is due to children missing their routine health care visits during the pandemic, and how much was the result of parents choosing not to vaccinate, Lontine said.

The state health department has been trying to reach parents who aren’t opposed to vaccines, but whose children don’t have all their shots. They’ve particularly focused on parents of children going into kindergarten, because starting school is a milestone and an opportunity to catch kids up, said Heather Roth, immunization branch chief at the Colorado Department of Public Health and Environment.

The state’s immunization records show about 6,000 children receive at least one shot after their parents got the text and email reminders, Roth said.

In September, the health department also started sending vans to schools and other places where families gather to offer the shots for free to children who are behind, Roth said. They provided more than 3,700 vaccines to 1,349 children, most of whom didn’t have a family doctor or usual source of care, she said.

“We’re trying to fill that gap,” she said.

Colorado has been lucky that no one has brought measles back to undervaccinated communities in recent years, Lontine said. Measles is one of the most contagious diseases that infect humans, and about 20% of unvaccinated people who get it need hospital care.