Measles is making a comeback: Can we stop it? - Harvard Health

Has the recent news about measles outbreaks in the US surprised you? Didn’t it seem like we were done with measles?

In the US, widespread vaccination halted the ongoing spread of measles more than 20 years ago, a major public health achievement. Before an effective vaccine was developed in the 1960s, nearly every child in the US got measles. Complications like measles-related pneumonia or hearing loss were common, and 400 to 500 people died each year.

As I write this, there have been 1,227 confirmed cases in 36 states, mostly among children. The biggest outbreak is in west Texas, where 97 people have been hospitalized and two unvaccinated school-age children recently died, the first measles deaths in the US since 2015. Officials in New Mexico have also reported a measles-related death.

Measles outbreaks are highly preventable. It’s estimated that when 95% of people in a community are vaccinated, both those individuals and others in their community are protected against measles.

But nationally, measles vaccination rates among school-age kids fell from 95% in 2019 to 92% in 2023. Within Texas, the kindergarten vaccination rates have dipped below 95% in about half of all state counties. In the community at the center of the west Texas outbreak, the reported rate is 82%. Declining vaccination rates are common in other parts of the US, too, and that leaves many people vulnerable to measles infections.

Only 3% of the recent cases in the US involved people known to be fully vaccinated. The rest were either unvaccinated or had unknown vaccine status (95%), or they had received only one of the two vaccine doses (2%).

As measles outbreaks occur within more communities, it’s important to understand why this happens — and how to stop it. Here are seven things to know about measles.

Several communities have suffered outbreaks in recent years. The measles virus readily spreads from person to person through the air we breathe. It can linger in the air for hours after a sneeze or cough. Estimates suggest nine out of 10 nonimmune people exposed to measles will become infected. Measles is far more contagious than the flu, COVID-19, or even Ebola.

It usually takes seven to 14 days for symptoms to show up once a person gets infected. Common early symptoms — fever, cough, runny nose — are similar to other viral infections such as colds or flu. A few days into the illness, painless, tiny white spots in the mouth (called Koplik spots) appear. But they’re easy to miss, and are absent in many cases. A day or two later, a distinctive skin rash develops.

Unfortunately, a person with measles is highly contagious for days before the Koplik spots or skin rash appear. Very often, others have been exposed by the time measles is diagnosed and precautions are taken.

Measles is not just another cold. A host of complications can develop, including

Complications are most common among children under age 5, adults over age 20, pregnant women, and people with an impaired immune system. Measles is fatal in up to three of every 1,000 cases.

During the latest outbreaks, 148 cases — about one in eight — have required hospitalization.

When you get sick from a viral or bacterial infection, antibodies created by your immune system will later recognize and help mount a defense against these intruders. In 2019, a study at Harvard Medical School (HMS) found that the measles virus may wipe out up to three-quarters of antibodies protecting against viruses or bacteria that a child was previously immune to — anything from strains of the flu to herpesvirus to bacteria that cause pneumonia and skin infections.

“If your child gets the measles and then gets pneumonia two years later, you wouldn’t necessarily tie the two together. The symptoms of measles itself may be only the tip of the iceberg,” said the study’s first author, Dr. Michael Mina, who was a postdoctoral researcher in the laboratory of geneticist Stephen Elledge at HMS and Brigham and Women’s Hospital at the time of the study.

In this video, Mina and Elledge discuss their findings.

Two doses of the current vaccine provide 97% protection — much higher than most other vaccines. Rarely, a person gets measles despite being fully vaccinated. When that happens, the disease tends to be milder and less likely to spread to others.

The safety profile of the measles vaccine is excellent. Common side effects include temporary soreness in the arm, low-grade fever, and muscle pain, as is true for most vaccinations. A suggestion that measles or other vaccines cause autism has been convincingly discredited. However, this often-repeated misinformation has contributed to significant vaccine hesitancy and falling rates of vaccination.

While news about measles in recent months may have been a surprise, it’s also alarming. Experts warn that the number of cases (and possibly deaths) are likely to increase. And due to falling vaccination rates, outbreaks are bound to keep occurring. One study estimates that between nine and 15 million children in the US could be susceptible to measles.

But there’s also good news: we know that measles outbreaks can be contained and the disease itself can be eliminated. Learn how to protect yourself and your family. Engage respectfully with people who are vaccine hesitant: share what you’ve learned from reliable sources about the disease, especially about the well-established safety of vaccination.

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

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