Measles has no treatments. Getting some may not be easy

backup plan – As vaccination rates slip, measles outbreaks are rising—yet there are no measles-specific antivirals and no clinical trials underway for treatments. Physicians can manage symptoms, but they cannot fight the virus itself. Researchers are now racing to build a “

When measles comes back, doctors can’t pull a cure off the shelf. There is no measles antiviral treatment—only symptom care for fever. fatigue. cough. and the rash that spreads from head to feet. For parents and clinicians watching vaccination rates loosen around the world. that gap has taken on an urgency that feels less academic and more immediate.

In a May 27 news briefing, Ruth Lynfield, an epidemiologist at the Minnesota Department of Health in St. Paul, said, “We haven’t had the need to develop measles antivirals. It hasn’t been a priority. I do think we need to invest in that now.” Her point lands sharply because measles has been kept at bay for years—largely because a highly effective vaccine has done the heavy lifting.

With two doses, the shot prevents about 97 percent of measles cases. When vaccination rates stay above 95 percent across a population. the virus struggles to break through. creating what is effectively a blockade of protection. That blockade protects people who can’t get the shot. including babies younger than a year old and people with compromised immune systems.

But the protection is fraying. Vaccination rates are slipping around the globe. including in the United States and Canada. as well as in some European countries. The backslide can be attributed in part to concerns about vaccine safety that are not supported by scientific evidence. as well as distrust of medical professionals and lack of access. Funding cuts for global aid could also lead to lower vaccination rates in regions where measles still circulates broadly. potentially setting the stage for future outbreaks.

In the United States, measles cases are already rising. This year, cases are poised to surpass last year’s count—the highest since 1991. Of the 2. 030 cases reported as of June 4. more than 90 percent have been in unvaccinated people or in people whose vaccination status is unknown. Officials say the country is at risk of losing its measles elimination status, after a “deluge” that began in January 2025.

Officials documented 2,288 cases in 2025, and as of June 4, there have already been 2,030 cases, with the column marked by an asterisk to denote partial year. Case counts in 2025 and 2026 are described as the largest in more than three decades.

One of the biggest misunderstandings about measles is that it’s “not that bad. ” Kathryn Hastie. a structural virologist at the La Jolla Institute for Immunology in San Diego. said. She argues the virus can cause complications that severely impact people’s lives, including pneumonia and blindness. Measles can erase immune memory, leaving people vulnerable to other infections. About 1 out of every 1,000 people infected with measles develop encephalitis, which can result in permanent brain damage. And 1 to 3 children, a group at high risk of measles, die of the disease for every 1,000 that are infected.

Antivirals and other treatments could help protect those who are vulnerable, but the research is limited. Getting drug candidates to market, researchers say, would be a bumpy road.

A key obstacle is that “Halting replication” fast enough may be crucial. One approach is repurposing drugs that work for other diseases—already approved drugs with broad antiviral activity. which could be rapidly deployed if proven effective against measles. But some researchers are trying to find something purpose-built.

Richard Plemper. a virologist and antiviral drug developer at Georgia State University in Atlanta. started using the measles virus as a tool to study how the immune system works in the early 2000s. around the time the United States achieved measles elimination. As measles remained a global problem. he said. “it actually became worthwhile to consider. do we maybe need a measles drug?”.

Studies had suggested a chemical probe designed to switch off certain viral functions. including replication. might be turned into an effective treatment. But because of the availability and potency of the measles vaccine. Plemper decided to search for a drug for the entire subfamily of viruses that measles belongs to. The Orthoparamyxovirus subfamily includes Nipah virus and two human parainfluenza viruses—also viruses that lack treatments.

Like many viral infections, including influenza, these viruses replicate and cause disease quickly. When a person becomes sick—typically several days after exposure—researchers say the window of opportunity for treatment is short. “The paradigm must be the earlier we treat, the better,” Plemper said. By the time someone is severely ill, the virus may already have stopped replicating, making antiviral treatment less effective.

Plemper and colleagues tested more than 100,000 potential compounds. One of them became the antiviral candidate GHP-88310. In ferrets infected with canine distemper virus. an Orthoparamyxovirus sometimes used as a proxy for measles in small mammals. the drug dampened viral replication when given daily starting three days after infection. In the work reported May 22 in Science Advances, all treated animals survived.

Plemper described how the drug works: by binding to a key viral protein. it “puts a foot on the brake.” He also emphasized that the target protein is important for replication across this subfamily of viruses. saying. “This compound is so attractive because it is equally effective against many of the related major human pathogens. of which measles is one.”.

He said the drug still has a long way to go before it could be used in people, but he hopes it could one day help people who aren’t vaccinated—perhaps even as a prophylactic to prevent measles after an exposure.

Another route is “A helping hand for the immune system.” Instead of stopping replication directly. researchers are looking at measles-attacking monoclonal antibodies produced in the lab. Hastie described monoclonal antibodies as “kind of an on-demand immunity.” Vaccines teach the body to recognize measles and build longer-term defenses over a few weeks. Monoclonal antibodies, by contrast, deliver immune-triggering proteins that get to work immediately.

As Hastie explained, “What we can do with monoclonal antibodies is essentially deliver hand-picked antibodies that are the best of the best to try and control the viral infection at the time of infection, either preexposure or post-exposure.”

Hastie and colleagues recently determined the structures of four measles antibodies from a vaccinated person. They then infused those antibodies into infected cotton rats and saw decreased amounts of measles virus in the rats’ lungs. The team reported May 7 in Cell Host and Microbe. One antibody even reduced the virus to an undetectable level. Because measles spreads through respiratory droplets, the findings suggest treatment could dampen transmission.

The work builds on studies of a different monoclonal antibody candidate called mAb 77. That antibody also diminished viral load in cotton rats, and it is undergoing additional testing in primates. Hastie said mAb 77 originated from a mouse. meaning using it in people requires tweaking the immune protein so that the body doesn’t treat it as a foreign invader. The four human antibodies from the new work wouldn’t require that step. The next step, researchers say, is testing in nonhuman primates.

There is a tradeoff. Hastie said monoclonal antibody treatment can be more expensive than an antiviral. But because antibodies are highly specific for their targets, she said the chance of side effects is low.

Still, even with promising lab and animal results, measles treatment faces a practical barrier: clinical trials. There are no clinical trials currently under way for measles treatments. Plemper said starting one could be difficult because enough cases are needed for a meaningful sample size. Trial logistics also require outbreaks to happen in predictable places and time windows.

With measles. Plemper said. “we don’t know exactly where the outbreaks will happen.” Thousands of people get sick with measles every year in some countries—Yemen. Pakistan. Sudan and others—but those cases are often tied to people lacking easy access to vaccines. “If you cannot reach the people for vaccination. then you would struggle to enroll them for a clinical trial. ” he said.

Funding is another concern. Plemper said few people might require treatment, which could make trials harder to support. Still, he noted that some U.S. biotech companies are taking steps to begin testing monoclonal antibodies. There is also an ethical problem: any unvaccinated children should be offered the vaccine rather than enrolled in a treatment trial.

Because of those hurdles. Plemper and his team are planning to test GHP-88320 on a different. but closely related. virus first: human parainfluenza virus type 3. Plemper described the virus as a “common virus” that infects people globally and is an “irritation” most of the time. causing mild. coldlike symptoms. But infections can be life-threatening for transplant patients whose immune systems are suppressed to lower the risk of organ rejection.

The goal is to see whether GHP-88310 could be helpful against that virus, which doesn’t have a vaccine. Because measles is in the same family of viruses, researchers hope it could ultimately be available for use during measles outbreaks too.

Late in the conversation, Plemper returned to the core lesson vaccination taught the world. “Vaccines, to some degree, fell victim to their own success,” he said. Preventing disease in the first place will always be the best approach, he added. But with antivirals and monoclonal antibodies as possible backup. he said. “Maybe we need this last kick to completely silence the virus.”.

measles vaccine antivirals monoclonal antibodies epidemiology outbreaks clinical trials Orthoparamyxovirus GHP-88310 GHP-88320 pneumonia encephalitis