What childhood vaccine rates can, and can't, teach us about COVID vaccines
Polls show Americans are increasingly interested in getting vaccinated against covid-19, but such surveys are largely national, leaving a big question: When the vaccines become available to the general public, will enough people get it in your county, city or neighborhood to keep your community safe?
Data on childhood vaccines, such as the one that protects against measles, mumps and rubella, provide hints. They show that the collective protection known as herd immunity can break down in pockets where not enough people choose to be immunized. Experts say at least 92% of the population must be vaccinated against measles to prevent it from spreading.
In the 2019-20 school year, for example, fewer than 5% of kindergartners in Colorado had an exemption from the MMR vaccine, a KHN analysis found. But the exemptions were not evenly distributed in the state: In schools with complete data, at least 15% had enough kindergartners with nonmedical exemptions — religious or personal — to leave them vulnerable to measles outbreaks.
Does childhood immunization data show us which communities will shun the covid vaccines? Maybe yes, maybe no. Vaccine hesitancy experts say the concerns some people have about the covid vaccines are not identical to those around childhood vaccines. So pockets of childhood vaccine refusal may not correspond to covid vaccine-hesitant pockets.
“The Venn diagram will have some overlap, but it wouldn’t tell us the whole story,” said Saad Omer, a vaccine researcher and infectious disease epidemiologist who directs the Yale Institute for Global Health. “It's not the same circle.”
Experts like Omer are worried, however, that the political divisions that arose during the pandemic, and are evident in attitudes toward the covid vaccines, could spread to other vaccination campaigns. Some of the same coalitions that, in recent years, fought expansion of childhood vaccination requirements in state legislatures around the country joined to fight covid lockdowns.
School immunization rates can shed light on how pockets of vaccine uncertainty work. Colorado is one of 15 states, according to the National Conference of State Legislatures, where parents can opt their children out of vaccines required for school entry for philosophical reasons. It stands to reason that, in those states, school immunization rates may provide a more unfiltered look at vaccine refusal than in others.
Research shows childhood immunization exemption rates tend to remain relatively stable within schools over time, according to Daniel Salmon, who directs the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health. A KHN analysis found that in Utah and Idaho, which have a decade of school-level MMR data, most schools with complete data had the same herd immunity status in 2018 as in 2009.
Kaiser Health News is an editorially independent news service. It is a program of the Kaiser Family Foundation, a nonpartisan health-care-policy research organization unaffiliated with Kaiser Permanente.