Decades after measles was declared eliminated in the United States, a resurgence in cases is causing disruptions in schools across the country, with a growing number of students sidelined by quarantines. But there has been little research into just how much these outbreaks are driving student absences.
A new study by Stanford researchers examined the effect one major measles outbreak in Texas this year had on attendance at a school district at the center of the event. The findings are striking: Absences increased 41% compared with the two prior years – an impact 10 times greater than expected for the number of reported infections.
The increase occurred among students at all grade levels but was more pronounced among younger students, climbing as much as 71% among preschool and kindergarten students.
The researchers attributed the unexpectedly high figure to precautionary absences – parents choosing to keep their children home, or schools excluding unvaccinated students – as well as a possible undercounting of infections.
The findings were released in a working paper posted on Dec. 17.
“In addition to the serious health risks from kids getting sick, this tells us that the lost learning time is really substantial,” said Thomas S. Dee, the Barnett Family Professor at Stanford Graduate School of Education (GSE), who co-authored the study with Sofia Wilson, a doctoral student at the GSE. “The declining school vaccination rates we’ve seen over the past few years are going to have real consequences for our children and our communities.”
A deadly contagion
The number of confirmed measles cases in the United States is higher this year than any year since the U.S. Centers for Disease Control and Prevention (CDC) declared the virus eliminated in 2000. The virus is highly contagious, infecting up to nine of 10 susceptible people exposed, and can be fatal for as many as three in every 1,000 children infected.
Cases have been confirmed this year across 43 states, with nearly half reported in Texas alone. One prominent outbreak took place in Gaines County, Texas, where the state health department announced a cluster of infections in January 2025 and formally declared a measles outbreak a week later.
The Stanford researchers filed a public records request with Seminole Independent School District, a public school district that serves 82% of the students in Gaines County, to get detailed data on student attendance for the 2022-23, 2023-24, and 2024-25 school years.
The data showed absences day by day in the district over the three-year period, allowing the researchers to identify attendance patterns unique to the school year, each month, and each day of the week, as well as seasonal patterns typically associated with student absences, such as the days before major school breaks.
They found that student absences at the onset of the outbreak in Gaines County were 41% higher than normal, accounting for variations in attendance they observed over the prior two years. Absences also increased significantly through each of the four remaining months of the school year, a pattern that corresponded with the timing of reported measles cases.
Based on county data tracking measles cases and the school district’s share of student enrollment, the researchers estimated 141 confirmed measles cases among the district’s students during the 2024-25 school year.
Because the state’s health guidance to schools recommended four days of isolation for students after the onset of a rash, the researchers estimated that at most there would be 564 days of absences among students with confirmed cases. But the 41% increase in absences translates to 5,822 missed days, roughly 10 times larger than what would have been expected based on known measles cases alone.
In this district, which serves nearly 3,000 students, there would typically be about 200 absences on a given day during the period from February through the rest of the school year, the researchers found. In those months following the 2025 outbreak, the district saw, on average, about 80 additional absences per day.
At the height of the outbreak, absences were equivalent to roughly 20% of the district’s overall enrollment, the study found.
Why absences matter
Attendance is “the most fundamental measure of student engagement,” the study authors wrote, citing evidence documenting the importance of school attendance for academic and other important life outcomes, such as employment and social development.
“Kids have to be in school to realize educational gains,” said Wilson, the study’s co-author and a former public school teacher, noting research that absences affect not only the students who miss school themselves but also their classmates, as teachers slow the pace of instruction overall to accommodate the absentees.
“We’re still reeling from the post-pandemic shock to attendance and achievement, and this may only exacerbate those impacts,” she said. “It’s unfortunate, because these events are preventable through vaccines.”
According to the CDC, when more than 95% of people in a community are vaccinated against measles, mumps, and rubella (MMR), most are protected through so-called “herd immunity.” In 2023, the national MMR vaccination rate for kindergarten students fell below that threshold, with 13 states even below 90%.
“If vaccine rates keep trending as they are currently, what occurred in Gaines County – and now South Carolina and other communities – will unfortunately be more common,” Wilson said.
