Plus a statewide map of school vaccination rates
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The Washington Post recently published an interactive article which shared immunization data collected from public schools in 34 states. The data shows plunging vaccine rates across the country.
I don’t doubt this basic finding, but the numbers they show for many schools in Milwaukee are incorrect when compared with the numbers published by the Wisconsin Department of Health Services (WI DHS). For many schools, the actual WI DHS immunization numbers are much higher.
For example, the Post article (whose data was also picked up by the Milwaukee Neighborhood News Service), reported that Neeskara Elementary had an MMR vaccination rate of 12% and an overall compliance rate of 7%. Fortunately, the real 2025 numbers for Neeskara, according to WI DHS, are an MMR rate of 60% and an overall rate of 50%. Given that herd immunity against measles requires “about 95% of a population to be vaccinated,” Neeskara is still disturbingly low, but there is a world of difference between 7% and 60%. Most of the children attending Neeskara have received this vaccine.
Neeskara is just one example where the Post story uses numbers much different than the latest from DHS. At MacDowell Montessori, the Post reported an MMR rate of 26% and an overall rate of 26%. The real numbers are 92% for MMR and 62% overall. Likewise, the Post data had Hayes Bilingual School at 33% for MMR and 27% overall. The real numbers are 76% MMR and 61% overall.
Overall, there are 155 schools for which the Post and WI DHS both provided data. In the WI DHS dataset, the average school’s compliance rate was 77% overall and 83% for the MMR vaccine specifically. This is 12 and 16 points higher, respectively, than the average in the Post data.
| Vaccine Compliance in Milwaukee Schools According to Data Collected by the Washington Post vs. Published by WI DHS | |||
| Washington Post Data | WI DHS data (2025) | WI DHS – WaPo | |
| Overall Compliance | 65% | 77% | +12 |
| MMR vaccination | 67% | 83% | +16 |
N.B. WI DHS top codes data at “>95%”. For the purposes of these averages, I treated those values as “95,” meaning that the true mean is slightly higher.
Why the errors?
What could explain why the Post data is so wrong for many schools in Milwaukee? I don’t know. My inquiries to the newspaper’s data team haven’t been answered—perhaps unsurprising, seeing as the paper just laid off one third of its staff. The answer is not that the Post data is from a prior year. Their data matches 2024 or 2023 WI DHS as badly or worse than the 2025 data.
The Post does cite the original data sources for their project. In Wisconsin, they list a data request to the state as their source. My best guess—and it’s only a guess—is that WI DHS originally supplied them with a file containing incorrect data. Then, at some point, WI DHS published the corrected data on their own website, but the corrected data never made it to the Post.
In my view, this episode is a demonstration of why research projects that collect data from dozens of different government sources are hard to do well. The biggest challenge to this kind of data analysis is not math or coding. It’s noticing and resolving the myriad unexpected data quality issues that can arise. When I looked at the Post data, I immediately searched for the schools closest to my house. Neeskara is one of them. I found the extraordinarily low vaccination rates reported there hard to believe, so I looked up the corresponding files on the WI DHS website and found the real, much more plausible numbers.
This kind of bespoke sanity testing is hard to do at scale, working under deadlines, and reconciling information in different formats from dozens of jurisdictions.
More details from WI DHS
Besides listing the MMR and overall vaccine compliance rates for each school, the WI DHS data also provides information about why students aren’t vaccine compliant. In most Milwaukee schools with low vaccination rates, the cause isn’t that parents have filled out vaccine waivers. According to the DHS statistics, it’s more common for students who are out-of-compliance to be classified as “in process,” “behind schedule,” or just “no record” rather than having explicitly opted-out of vaccinations by completing a waiver.
At Neeskara, for example, 20% are “behind schedule” and 28% have “no record.” Scarcely any students actually have a vaccine waiver on file. Similarly, Riverside High School has truly dismal 12% vaccine compliance rate. Eighty percent of its students are “behind schedule” and 7% are “no record.” Few, if any, have waived vaccine requirements.
Schools where many students have waived vaccines are uncommon, but they do exist. At Tamarack Waldorf, on Milwaukee’s East Side, 67% of students have met minimum vaccination requirements. Sixteen percent have “waived all vaccines” and 24% have completed a “personal conviction waiver.” The distinction between these classifications is unclear to me. So is the distinction between students who are listed as “in progress” vs. “behind schedule.”
In general, the quality of the school-level data provided by WI DHS raises as many questions as it answers. At North Division, for instance, 65% of students were classified as “met minimum requirements” in 2024, with just 5% having “no record.” The next year, in 2025, fewer than 5% “met minimum requirements” and 80% had “no record.” Absent some extraordinary turnover over students between those two years, I struggle to imagine how this could be possible. More likely: the data was reported incorrectly in one or both of the years.
Many schools also fail to submit their reports every year. In 2025, 377 schools statewide (13% of the total) failed to submit a report. But 197 of those schools had submitted a report the previous year, in 2024.
The current self-reported school vaccination data collected by WI DHS is incomplete and inconsistent where available. The failure to report this data accurately (or at all) poses real challenges to public health efforts. A health department might want to plan its vaccine outreach campaigns around those schools where children are unvaccinated, not because their parents have opted them out of immunizations, but simply because those children are apparently not receiving medical care. Better data would improve this kind of targeting.
I’ve built an interactive map showing the available data for every school in the state. Click the image below to open it. Mousing over each school will reveal its name and 2025 overall vaccine compliance rate. Click the school to display a table showing more detailed vaccine statistics for each year from 2022 through 2025. If the school failed to submit a report in any of those years, all values for the year will be NA.
