When Dr. Jessica Cataldi, a professor of pediatrics at the University of Colorado School of Medicine and a practicing pediatrician at Children’s Hospital Colorado, was doing infectious disease work in Africa years ago, she noticed a difference in how many parents there thought about vaccines.
Resistance to vaccination exists across the world for a variety of reasons — from spiritual belief to experiences with prior botched vaccination campaigns. But Cataldi said parents were generally more willing to vaccinate their kids when the diseases were active threats in their communities, meaning their children might get sick without a vaccination.
Back home in the United States, vaccines have largely eradicated infectious diseases of the past — like measles and polio — and that, too, has shaped how parents view vaccines, Cataldi said.
“It’s a difference thinking about the risks and benefits,” she said. “People who see kids getting sick more often, they understand the risk from those diseases. When the diseases are less common, there is a shift to thinking more about the risk of the vaccine.”
That insight helps explain Colorado’s arduous struggle to get childhood vaccination rates above 90% statewide, a goal achieved this year just before the coronavirus pandemic hit and likely knocked them back down again. But it also provides a hint at one of the biggest unknowns surrounding vaccines for COVID-19 that are fast heading toward market: Once they’re approved, how many people will actually want to use them?
Because it is possible that the coronavirus vaccines won’t be 100% effective for everyone, their value may lie more in their ability to bring an entire population to the level of herd immunity — where not everybody is immune but just enough are to prevent the virus from spreading. But reaching herd immunity through a partially effective vaccine requires lots of people to get vaccinated. And Colorado’s struggle with childhood vaccination rates shows why that could be difficult.
For years, Colorado has ranked among the lowest in the nation for the vaccination rates of kindergartners.
Last school year, the rate of measles vaccination for Colorado kindergartners was around 87%, two full percentage points below the second-lowest state, Idaho, according to the federal Centers for Disease Control and Prevention. Colorado was the lowest in the country for the chickenpox vaccine, the polio vaccine and the hepatitis B vaccine and second-lowest for the DTaP vaccine, which protects against diphtheria, tetanus and whooping cough.
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