Though a measles vaccine has existed for more than 60 years, much still remains unknown about how exactly the shot generates protection against the virus. Now, scientists have turned to the immune systems of vaccinated people to dig up answers—and their findings may lead to new medicines against the resurgent disease.
“It’s stunning, isn’t it?” Erica Ollmann Saphire, Ph.D., a structural biologist at the La Jolla Institute for Immunology who led the study, told Fierce Biotech. “In 2026, we do not know what the human antibodies against the measles virus are.”
By analyzing the blood of 20 people previously given the measles, mumps and rubella (MMR) vaccine, researchers identified four promising antibodies that cling to the measles virus’ surface and prevent it from infecting cells. The work was published today in the journal Cell Host & Microbe.
These samples were left over from research done during the COVID-19 pandemic, Saphire explained. Finding antibodies from these samples that attach to measles was relatively straightforward, she said, because measles doesn’t have as thick a protective shield of sugar molecules around it as other viruses do.
It’s likely that no one else had bothered to seriously study how the measles vaccine works because modern tools weren’t available when the vaccine debuted in 1963, Saphire suggested, and because the disease was considered “to be a problem that was solved.”
Saphire’s team settled on four promising antibodies, which they could visualize using cryo-electron microscopy. Two of the antibodies target measles’ hemagglutinin surface protein, which the virus uses to attach to cells, while the others bind to the fusion protein, used to physically pierce the cell to grant the virus entry.
The F protein “springs forward in an irreversible way, like a spearfishing rod, to change shape and drive itself into your human cell,” Saphire said.
The antibodies were able to halt virus replication in cotton rats when given either before or as long as two days after exposure to measles. The researchers now plan to find a partner, in industry or the non-profit sector, to advance the antibodies through preclinical testing and into the clinic, Saphire said.
“I fully believe that these antibodies have a good chance to be effective when given prophylactically,” Richard Plemper, Ph.D., a biomedical scientist at Georgia State University who was not involved with the new study, told Fierce. But he cautions that the cotton rat isn’t a good model for post-exposure studies because the disease progresses differently in rodents than it does in humans.
“I caution against drawing conclusions about therapeutic potential against [measles virus] in humans based on cotton rat data,” Plemper said.
Other models for measles exist, including non-human primates and ferrets infected with a related virus called canine distemper. Which one is best depends on the question you are asking, Stefan Niewiesk, Ph.D., an animal model developer and virus researcher at Ohio State University, who worked on the new study, told Fierce.
“If you want to select highly effective antibodies and gain some indirect evidence for its potential clinical effect, then the cotton rat is useful,” Niewiesk said. “It is an infection model, not a disease model.”
For Niewisk and Saphire’s study, they considered therapeutic treatment to mean that the antibodies reduced viral replication if injected after infection, Niewiesk added.
There are currently no approved antibodies or antivirals for measles. Plemper, too, is working on some potential antiviral options, which target the machinery used by the virus to copy its genome. This approach could be used in tandem with antibodies, Saphire said.
Though the MMR vaccine is safe and effective, not everyone is able to safely take it, including infants under the age of 12 months and those who are immunocompromised. Worldwide, there are still more than 10 million cases of measles every year, and Canada has just lost its elimination status for the disease, with the U.S. likely set to join its northern neighbor soon.
Long-acting preventive antibodies are already used to protect babies against respiratory syncytial virus, including Sanofi and AstraZeneca’s Beyfortus and Merck’s Enflonsia. These antibodies are engineered to last longer in the human body to provide many months of protection, and a similar approach could be used with the newly identified measles antibodies, Saphire said.
“We're talking about keeping babies alive and protecting kids with cancer,” Saphire said. “There's definitely a place for a backup way to prevent measles infection or to treat measles infection in this day and age, and we've got the ability and the tools to do it.”