The NIH Just Redefined What Counts as a Clinical Trial—Here's Why It Matters for Research

The National Institutes of Health (NIH) announced a major policy shift in January 2026 that fundamentally changes how certain human research studies are classified. Starting May 25, 2026, Basic Experimental Studies Involving Humans (BESH)—research that explores fundamental biology or behavior without immediate clinical applications—will no longer be classified as clinical trials. This means thousands of basic science projects will no longer need to register on ClinicalTrials.gov or report their results there.

What Exactly Changed in the NIH's Definition?

For over a decade, the NIH's 2014 policy cast a wide net when defining clinical trials. Any study that prospectively assigned human participants to interventions to evaluate health-related outcomes was classified as a clinical trial, regardless of whether the research aimed to improve patient care or just understand how the brain works. This broad definition was meant to increase transparency and accountability in federally funded research, but it inadvertently swept in basic science projects that had nothing to do with testing therapies or changing medical practice.

BESH studies are fundamentally different from clinical trials. They focus on uncovering how biology and behavior actually work—exploring questions like how the brain processes information or how people make decisions in controlled laboratory settings. While this research might eventually contribute to medical breakthroughs down the road, it's not designed to test treatments or directly improve health outcomes. The NIH recognized this distinction and decided these studies shouldn't be burdened with the same registration and reporting requirements as drug trials or medical device studies.

What Are the Practical Changes for Researchers?

The reclassification affects how researchers manage their work and funding. Here's what's shifting:

• Registration Requirements: BESH studies will no longer be required to register on ClinicalTrials.gov, the federal database where clinical trial information is publicly tracked and results are reported.
• Funding Opportunities: The NIH plans to retire BESH-specific funding announcements after May 25, 2026, allowing basic science researchers to submit proposals under "Clinical Trials Not Allowed" funding categories instead.
• Existing Projects: Studies already underway will continue operating under their current award terms, with interim flexibilities from a prior notice still in effect until the transition is complete.

For researchers planning human-participant studies, the NIH recommends consulting updated decision tools on its website and contacting program officers for guidance on how this change affects their specific projects.

Why Does This Matter for the Broader Research Landscape?

The scale of clinical research is substantial. As of the end of 2025, ClinicalTrials.gov contained a cumulative total of 563,835 registered studies, with 42,969 new studies posted that year alone. In 2026, over 7,000 additional studies have already been registered. This reclassification streamlines the system by removing administrative burden from basic science research while keeping the spotlight on applied clinical research where transparency is most critical for patient safety and public health.

"It's essential for the U.S. government to strengthen the clinical trial industry by providing clear definitions," said Don Ward Hackett, publisher of Vax-Before-Travel.com. "Over the past 35 years, we have seen numerous adjustments with the clinical trial industry integrating digital technologies, and we are very optimistic that these changes will enable the vaccine industry to produce world-class products by 2026".

The policy shift also reflects a broader recognition that not all human research serves the same purpose. By distinguishing between basic science exploration and clinical applications, the NIH can focus its transparency and accountability mechanisms where they matter most—on studies that directly test treatments, devices, or interventions intended to change medical practice. This allows basic researchers to pursue fundamental questions about human biology and behavior without unnecessary bureaucratic overhead, while ensuring that clinical trials remain rigorously tracked and reported to the public.

Researchers should note that the May 25, 2026 deadline applies to grant applications due on or after that date. The NIH will provide further instructions regarding application systems and funding announcements as the deadline approaches, so staying informed through official NIH communications is important for anyone planning human-participant research.