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YOUR PERSONALIZED CANCER VACCINE

Scientific American

December 2025

Vaccines based on mRNA can be tailored to target a cancer patient's unique tumor mutations. But crumbling support for cancer and mRNA vaccine research has endangered this promising therapy

- BY ROWAN MOORE GERETY ILLUSTRATION BY TAVIS COBURN

AS SOON AS BARBARA BRIGHAM'S CANCEROUS PANCREATIC TUMOR was removed from her body in the fall of 2020, the buzz of a pager summoned a researcher to the pathology department in Memorial Sloan Kettering's main hospital in New York City, one floor below. Brigham, now 79, was recovering there until she felt well enough to go home to Shelter Island, near the eastern tip of Long Island. Her tumor and parts of her pancreas, meanwhile, were sent on an elaborate 24-hour course through the laboratory. Hospital staff assigned the organ sample a number and a unique bar code, then extracted a nickel-size piece of tissue to be frozen at -80 degrees Celsius. They soaked it in formalin to prevent degradation, then set it in a machine that gradually replaced the water in each cell with alcohol.

Next, lab staff pinned the pancreas to a foam block, took high-resolution images with a camera fixed overhead and used a scalpel to remove a series of sections of tumor tissue. These sections were embedded in hot paraffin and cut into slices a fraction of the thickness of a human hair, which were prepped, stained and mounted on glass slides to be photographed again. By the time a pathologist looked at Brigham's tumor under a microscope the next day, more than 50 people had helped steer it through the lab. Still, this work was all a prelude.

The real action came some two months later, when Brigham returned to the hospital to receive a vaccine tailored to the mutations that differentiated her tumor from the rest of her pancreas. Made of messenger RNA (mRNA) suspended in tiny fat particles, the vaccine was essentially a set of genetic instructions to help Brigham's immune system go after the mutant proteins unique to her tumor cells. It was, in other words, her very own shot.