Tracking the drop in U.S. childhood vaccinations: Our methodology

Editor’s note: This 2026 NBC News data investigation is an update of The Vaccine Divide, which was originally published in September 2025.The methodology for both projects is similar.

The new data was collected from June to October 2026.For SubscribersFOR SUBSCRIBERSRon DeSantis makes his first move toward a possible presidential runFOR SUBSCRIBERSTrump’s DOJ says its mission is ‘unchanged’ after GOP’s midterm losses FOR SUBSCRIBERSThe House districts that remain uncalled after the 2026 midtermsFOR SUBSCRIBERSU.S.on verge of losing measles-free status as cases surgeFOR SUBSCRIBERSMAHA rejoices as Stephen Miller takes over as chief of staffFOR SUBSCRIBERSOne idea with universal appeal for Democrats: Get Elon Musk under oathFOR SUBSCRIBERSHow the Kremlin turned out the lights at Russia’s top independent newspaperFOR SUBSCRIBERSThe Data Dive: Steve Kornacki analyzes Texas’ big blue shiftFOR SUBSCRIBERSFederal chip smuggling probe shifted after Nvidia contacted investigatorsFOR SUBSCRIBERSTrump inadvertently led emissions to fall by going to war with Iran, research showsFOR SUBSCRIBERSHow Congress’ post-midterms session is shaping upFOR SUBSCRIBERSBig tasks await as Congress returns after Democratic surgeFOR SUBSCRIBERSThey fled Democratic-run states to escape liberal policies.

Then the blue wave hit.FOR SUBSCRIBERSOregon man charged with taking Utah teen had been accused of sexually abusing 6-year-oldFOR SUBSCRIBERSU.S.skips the COP31 climate summit as 1.5C global warming limit slips awaySlide 1 of 1For “The Vaccine Divide,” NBC News gathered massive amounts of data from state governments and archives of public records.

With the help of infectious disease researchers at Stanford University, NBC News filed scores of requests for documents, including materials obtained under the Freedom of Information Act, and wrestled different types of data into a standardized format to map and compare rates across thousands of counties.MethodologyHow NBC News co...