Measles: What you need to know

There is a resurgence of measles cases and outbreaks in the United States. As of August 6, 2025, the CDC has confirmed 1,356 measles cases in 40 states, and experts point to declining MMR vaccination rates in some groups and communities as the cause.

Dr. Thomas Boyce, pediatric infectious disease specialist at Marshfield Children’s, provided key facts regarding measles.

What you should know about measles:

Measles spreads person-to-person primarily via droplets from being near someone with measles when they cough or sneeze. In addition, measles can be transmitted via the airborne route: the virus remains in the air for at least two hours after an infectious person leaves the area. Direct contact with the patient’s secretions can also transmit the virus.
Measles is one of the most contagious viruses in the world. It spreads through the air and can linger in a room for up to two hours after an infected person has left. Even brief exposure can lead to infection in unvaccinated individuals.
Symptoms appear 7-14 days after contact with the virus and typically include high fever, cough, runny nose and watery eyes. A rash appears 2-4 days after the first symptoms.
Measles can be very serious. One in 20 people with measles will develop bacterial pneumonia. For every 1,000 people infected, one or two people will die as a result.
The infection often enters the U.S. through unvaccinated international travelers. Make sure you are vaccinated before traveling internationally.
If an unvaccinated person is exposed to measles, giving them the MMR vaccine within 72 hours of exposure can prevent them from becoming infected.

Measles (MMR) vaccine provides protection

You can prevent measles by a safe and effective vaccine. This vaccine is part of the routine, recommended childhood vaccine schedule. Vaccines have saved millions of lives and many studies have confirmed that there is no link between measles-mumps-rubella (MMR) vaccine and autism.

In most cases, if patients have not received the MMR vaccine, CDC recommends vaccination. Patients should talk to their provider about any questions regarding measles vaccination.

Health care providers recommend children receive the MMR vaccine at ages 12-15 months and again at 4-6 years before starting school. Two doses of the MMR vaccine are 97% in preventing measles and offers lifelong protection. One dose is about 93% effective. In rare cases of measles occurring post-vaccination, symptoms are usually mild.

Children 6-12 months old can receive the vaccine if they will be traveling internationally or to an area within the U.S. where measles cases are occurring. It is not approved for children less than six months old.

“MMR is a live-attenuated vaccine. Young infants, pregnant women, and people with weakened immune systems cannot receive the vaccine,” said Dr. Boyce. “They depend on others around them to receive vaccinations to keep them safe.”

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Don’t rely on natural immunity for measles

Natural immunity is your body’s ability to recognize and fight off infections after being exposed to a virus. It involves producing antibodies and memory cells that help defend against future infections.

Natural infection with measles can lead to lifelong immunity, however the risks of getting the disease far outweigh the benefits, especially when a safe, effective vaccine is available.

“Relying on natural immunity for measles means risking serious complications, hospitalization, and even death,” said Dr. Boyce. “The vaccine offers the same long-term protection, without the danger of the disease.”

Here’s why natural infection is not a safe strategy:

Severe complications are common. One in 20 people with measles will develop pneumonia, and one to three in every 1,000 will die from the disease.
It’s highly contagious. Measles can spread rapidly in communities with low vaccination rates, putting infants, immunocompromised individuals, and others at risk.
Outbreaks are resurging. In 2019, the U.S. saw its highest number of cases in nearly 30 years. Now, in 2025, more than 1,356 cases were confirmed in the U.S., including in Wisconsin.
Vaccination is highly effective. The MMR vaccine is 97% effective after two doses and provides lifelong protection in most people. One dose is 93% effective.

“Choosing vaccination over natural infection is not just about protecting yourself, it’s about protecting your community. The MMR vaccine is a proven, safe, and essential tool in preventing the return of a disease we have the power to control,” said Dr. Boyce.

For questions about the measles vaccine, talk to a Marshfield Children’s provider.

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