Associate Professor Dr. Margaret Doll directs the ACPHS Public Health program. She spoke to us about her research on vaccinations in light of the current measles outbreak in the Southwest.
Federal health officials declared in 2000 that measles had been eliminated from the U.S. Today, in the nation’s Southwest, we have the worst single outbreak of the disease since that time. What do you see as the key factors contributing to the disease’s return?
Although most U.S. children are vaccinated for measles, we have seen small declines in childhood measles vaccinations following the COVID-19 pandemic. For example, prior to the pandemic, approximately 95% of U.S. kindergarteners were vaccinated for measles, but now coverage is approximately 93%.
Since measles is so infectious, even a small decrease in measles vaccine coverage matters. Because measles still circulates in other countries in the world, cases of measles are frequently imported into the U.S. Experts estimate that 95% of the population needs to be vaccinated to stop measles from spreading. Therefore, these declines in U.S. measles vaccine coverage to levels below 95% mean that there are now more opportunities for imported cases to spread to non-vaccinated, non-immune people, leading to a greater potential for larger U.S. outbreaks and sustained transmission.
How serious a threat is measles to public health? What are the risks of having the disease spread through large swaths of the country?
For some people — even those without other underlying conditions — measles can be a severe disease that leads to very serious complications. For example, approximately one in five children who contract measles will be hospitalized, one in 20 will develop pneumonia and up to three in 1,000 children with measles will die from their infection.
When many people are infected with measles in our population, the number of people who experience these severe complications grows. Tragically, in the current outbreak, we have already seen two children die from a measles infection, and public health officials fear with continued measles spread we may see more. These outcomes are particularly sad because they are entirely preventable; we have a well-established safe and effective vaccine that can prevent measles and these severe outcomes.
What are some factors that contribute to measles under-vaccination?
There are a lot of reasons that people may not receive a measles vaccination. For some children, it may be a lack of access to health care, health-care costs or even the inconvenience of getting vaccinated when measles may not be perceived as a high threat. For others, hesitancy to get vaccinated may stem from concerns about vaccine safety or effectiveness. With the COVID-19 pandemic, we have unfortunately seen all these factors exacerbated, which has contributed to the declines in childhood measles vaccination.
What has your research revealed about factors that influence people’s decisions to get vaccinated against measles?
My research suggests that a measles outbreak can motivate some individuals to get vaccinated. Specifically, my lab examined the relationship between a large national measles outbreak that began at the Disneyland theme park in California in 2014 and subsequent vaccination rates; we found that U.S. childhood measles vaccinations increased following the outbreak. However, these increases were not universal among all U.S. subpopulations, which demonstrates that factors that motivate some people to get vaccinated may not be effective or motivating for everyone.
What current vaccine-related research are you engaged in?
Currently, my lab is working to better understand the effects of different laws and policies on vaccine uptake. For example, we recently examined the effect of a New York law that eliminated religious exemptions for school-mandated vaccines. We found the law was effective in increasing vaccine coverage among students who attended New York schools. This research is important because it helps public-health practitioners and policymakers better understand the effects of vaccine laws and policies, and how susceptible our population is to vaccine-preventable disease outbreaks.
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