Lethal spread this year measles in rural West Texas and other parts of the United States was a stark warning about how defenses against deadly childhood diseases are weakening across the country.
That was the key finding of a six-month investigation by NBC News, conducted in collaboration with Stanford University, that produced the most comprehensive analysis to date of vaccinations and school benefits.
NBC News has collected vast amounts of data from state governments and public records archives going back years or decades. With the help of infectious disease researchers at Stanford NBC News has filed numerous document requests, including material obtained under the Freedom of Information Act, and has compiled various types of data into a standardized format to map and compare metrics across thousands of counties.
The analysis found that a large portion of the U.S. population currently lacks the basic, ground-level immunity that medical experts say is needed to stop the spread of measles, which was once a thing of the past.
NBC News Data Investigation: How Progress Against Childhood Diseases Is Rolling Back.
The idea for the project grew out of a conversation about how to cover changes in vaccine policy and opinion between NBC News' health and medical team and Dr. Peter Hotez, a vaccine expert and dean of the National School of Tropical Medicine at Baylor College of Medicine in Dallas.
The conversation led to infectious disease scientist Dr. Nathan Law of Stanford University, who compiled a data map of vaccinations and vaccine exemptions in several states. Lo co-authored the months-long data collection project, helping to highlight the limitations of broader state-level vaccination trends collected by the Centers for Disease Control and Prevention.
Outbreaks start locally.
We're putting vaccination trends under the microscope, down to the county level. The results could help public health officials better predict where the next outbreak might occur and how best to allocate resources to stop it.
Or parents of children at high risk for complications from infectious diseases could find out whether their community is a potential hot spot.
The analysis revealed unexpected trends.
For example, St. Louis, a large metropolitan area with a diverse population, has seen declining immunization rates. That's why this is the main focus of reporting.
The findings reveal a fissure in an already fragmented society: the vaccine rift.
Our methodology
How NBC News collected data
NBC News created a database of vaccinations and child care benefits using data provided by state governments, primarily health agencies. The data combines publicly available information available for some states and data provided directly to NBC News.
The data covers vaccinations of children in kindergarten for each school year.
Once collected, the data was collated and tax exemption rates were calculated for subsequent analysis. The analysis focuses on four aspects of the data:
- Medical Exceptions: Exceptions are provided if students have a medical condition that could make vaccination potentially harmful.
- Non-medical exceptions: Exceptions for students who refuse required immunizations due to personal or religious beliefs.
- MMR (Measles-Mumps-Rubella) Vaccination: For states that separate data by number of doses, MMR vaccination is counted by the second dose.
- Up-to-date immunizations: Students are considered immunized if they have received the full series of immunizations required for enrollment in school.
How the data was processed
Given the patchwork of formats, jurisdictions, and data collection methods across states, this task required extensive work to ensure that potential data inconsistencies were resolved.
- Some states, such as Ohio and New York, required additional calculations to aggregate data provided by the state.
- Other states required manual entry of hundreds of rows of tabular data.
- All data has been checked for accuracy.
Data Analysis
Each state collects data differently. Some use health districts instead of counties. Some states provided more than a decade of data, others only two years. Some states have redacted certain data for privacy reasons.
- Not all states have the latest data. Florida has not provided data on kindergarten exemptions after the 2021-2022 school year. Montana stopped collecting data on vaccines and exemptions after 2019, first due to Covid and then due to the passage of a state law (HB 334) in 2021, which eliminated the state's obligation to collect vaccination data.
- Some states (such as Arizona, Colorado, and Minnesota) do not collect overall “up-to-date” data showing the percentage of kindergarten teachers who have completed all required vaccinations. Others (such as Florida, New Hampshire, New Jersey and South Carolina) provided only “current” numbers.
- Other states—Mississippi, New Hampshire and South Carolina—provided data only for grades K-12 and not specifically for kindergarten. West Virginia also falls into this category based on its tax exemption data. Mississippi could only share pre-K-12 exemption data.
- Some states—Illinois and New York—do not collect grade-level data, so the data refers to elementary schools in general (pre-K-8 for Illinois, New York is based on New York State Department of Education labeling of elementary schools) rather than kindergartens specifically. Hawaii also fell into this category (up to K-5) because school-level data was more consistent than kindergarten data.
- Other states did not provide county-level data. Alaska, Kansas, and Nebraska provided data for other jurisdictions. Delaware and Rhode Island provided state-level data only. Indiana was unable to provide county-level exemption data. West Virginia was unable to provide immunization data at the county level.
- Some states (such as Michigan) collect data by calendar year rather than school year.
- Wyoming did not report consistent data among kindergarteners, so the most consistently reported value was used instead: one dose of MMR among children aged 19 to 35 months. Accordingly, exclusions for children under 5 years of age were used to accommodate this age group.
- West Virginia has been unable to provide immunization data at the county level, but has been able to provide county-by-county exemption data since the issuance of Executive Order 7-25 in January, which overturned the state's long-standing ban on non-medical exemptions.
- Alaska was unable to provide regional data on exemptions due to privacy concerns due to small sample size.
