WASHINGTON (AP) — A first-of-its-kind cancer vaccine is significantly reducing the chances that melanoma patients’ tumors come back, according to results of a major study released Thursday by drugmakers Moderna and Merck.

The vaccine was custom-brewed for each patient to match their tumor. Adding it to a standard post-surgery treatment reduced by 42% the risk of melanoma returning two years after surgery, according to the most advanced study to date of this new strategy for fighting cancer.

“The field has been looking for a win and I think this one is a big one,” said Dr. Hussein Tawbi of MD Anderson Cancer Center in Houston, one of the researchers in the international study.

The vaccine, called intismeran, is made with the same Nobel Prize-winning mRNA technology that was behind COVID-19 vaccines.…