Moderna announced Thursday that an experimental cancer vaccine it is developing with Merck – when combined with the latter’s Keytruda immunotherapy – has been proven in a clinical trial to cut the risk of recurrence or death from the "most serious form of skin cancer" by half after three years. 

The company, citing data from a trial involving 157 patients with "high-risk stage III/IV melanoma," said the combination of treatments "reduced the risk of recurrence or death by 49%" compared to those just taking Keytruda alone. The results also showed the combination lowers the chances of melanoma spreading elsewhere in the human body by 62%, according to Moderna. 

"We are committed to driving research forward for innovative modalities in earlier stages of cancer, where we can make the most meaningful impact for patients, by combining Merck's expertise in immuno-oncology with Moderna's innovative mRNA technology," Marjorie Green, the senior vice president and head of late-stage oncology at Merck Research Laboratories, said in a statement. 

Moderna said the most common side effects of people in the trial were "fatigue (60.6%), injection site pain (56.7%), and chills (49%)." 

"The rates of melanoma have been rising over the past few decades, with nearly 325,000 new cases diagnosed worldwide in 2020. In the U.S., skin cancer is one of the most common types of cancer diagnosed, and melanoma accounts for a large majority of skin cancer deaths," it also said. "It is estimated there will be nearly 100,000 new cases of melanoma diagnosed and almost 8,000 deaths resulting from the disease in the U.S. in 2023." 

The American Cancer Society says melanoma is a type of skin cancer "that develops when melanocytes (the cells that give the skin its tan or brown color) start to grow out of control. 

"Melanoma is much less common than some other types of skin cancers," according to the organization. "But melanoma is more dangerous because it’s much more likely to spread to other parts of the body if not found and treated early." 

Reuters reports that Moderna is currently building a facility in Massachusetts to produce the experimental vaccine at a commercial scale and is hoping to have the property completed by next year. 

Moderna President Stephen Hoge told the news agency that despite Thursday’s data release, it will still take some time before the companies can file for approval for the treatment.