Measles Outbreak Highlights Eroding Immunity in the U.S.

This year’s concerning rise of measles in rural West Texas and several other regions across the U.S. serves as a stark reminder of the declining protection against serious childhood illnesses nationwide.

This conclusion emerged from a comprehensive six-month investigation by NBC News, conducted in collaboration with Stanford University, marking the most detailed study of vaccination rates and school exemption policies to date.

By amassing a vast amount of data from state agencies and historical public records, NBC News, alongside infectious disease researchers at Stanford, submitted numerous requests for documents. This included materials obtained via the Freedom of Information Act, as they worked to standardize various data sets to effectively analyze and compare vaccination rates across thousands of counties.

The study revealed a troubling reality: a significant portion of the U.S. population lacks the baseline immunity deemed necessary by health experts to curb the spread of measles, which had largely been controlled in the past.

NBC News Data Investigation: Understanding the Backslide on Childhood Illnesses

The project began after a discussion about shifts in vaccine policy and public perception, involving the NBC News Health and Medical team and Dr. Peter Hotez, a prominent vaccine expert from Baylor College of Medicine in Dallas.

This dialogue led to collaboration with Dr. Nathan Lo at Stanford University, who had already analyzed vaccination and exemption data in several states. His involvement proved crucial in identifying the gaps in the broader vaccination trends tracked by the Centers for Disease Control and Prevention.

Local Outbreaks and Their Implications

By scrutinizing vaccination trends at the county level, the findings aim to assist public health officials in anticipating potential outbreaks and directing resources effectively. This information could be invaluable for parents of children more vulnerable to infectious diseases, helping them understand if they live in areas of concern.

The analysis uncovered unexpected patterns. For instance, St. Louis, a significant urban hub known for its diversity, is currently experiencing a decline in immunization rates, which makes it a focal point for these reports.

These revelations expose a fracture in an already divided society: what some have termed the “vaccine divide.”

Methodology Behind the Investigation

In constructing a database of vaccination and exemption records for kindergarteners, NBC News relied on data from state health agencies. The collected information includes public records from various states and additional direct data submissions.

This database covers kindergarten vaccination statistics for each academic year.

Once the data was gathered, calculations were made to determine exemption rates for analysis. The investigation concentrated on four key components:

1. Medical exemptions: Granted for students with health conditions that could be aggravated by vaccinations.
2. Nonmedical exemptions: For those opting out of vaccinations due to personal or religious beliefs.
3. MMR (measles-mumps-rubella) vaccinations: Where applicable, this was tracked by the second dose.
4. Up-to-date vaccinations: Students deemed “up-to-date” are those who have received all required vaccinations for school enrollment.

Data Processing Challenges

The varying formats and collection methods across states required rigorous work to reconcile potential discrepancies in the data.

• For states like Ohio and New York, further calculations were needed to compile the data.
• Other states necessitated manual entry of extensive tables.
• Every piece of data underwent thorough checks for accuracy.

Analyzing the Data

Different states have diverse methods of data collection. Some rely on health districts instead of counties, while certain states provided extensive historical data, while others limited it to a couple of years. Privacy concerns led to some redactions.

• Not all states offer updated data; for example, Florida stopped sharing kindergarten exemption figures post-2021-2022, and Montana ceased its collection after 2019.
• Some states do not report the overall “up-to-date” vaccination figures, complicating the understanding of the vaccination landscape.
• Certain states provide data for K-12 rather than specifically for kindergartners, further complicating the analysis.
• Counties in multiple states may also lack comprehensive data, hindering the ability to draw clear conclusions.
• Issues also arise as some states collect data on a calendar-year basis rather than by school year.
• Inconsistent reporting from states means relying on the most reliable information available is necessary.
• Alaska faced privacy issues due to small sample sizes, limiting the disclosure of regional exemption data.