Updated on June 21, 2024.
Measles is an infection caused by a virus. It is spread very easily between people. It can lead to serious health issues. It can be deadly.
The first measles shot was used in the U.S. in 1963. Before that, about three to four million people in the U.S. got measles each year. About 48,000 needed hospital care. Up to 500 died. Most were children who were healthy.
The measles shot stops the spread of this infection. By 2000, measles was mostly gone from the U.S.
But measles can come back. In recent years, cases of measles have been rising. The COVID pandemic caused delays in getting the shot. Choosing not to get the shot plays a role, too.
Decades of studies show the measles, mumps, and rubella (MMR) shot is very safe. It is highly effective. The MMR shot protects against three different viruses.
The most common side effects from the shot are:
- Mild rash
- Fever
- Achiness in the arm where the shot was given. This lasts a short time.
Here’s what to know about measles.
Measles has early signs
Early signs of measles come in stages. These are:
- Fever and fatigue. These start seven to 14 days after getting infected.
- Cough and runny nose start soon after that.
- Conjunctivitis may start, too. This is when the whites of the eyes turn red or pink.
- About two days later, tiny white spots form inside the mouth. These are called Koplik spots.
- Three to five days after symptoms first appear, a measles rash starts. This is red. It starts on the face. It spreads down to the chest, arms, legs, and feet.
- A very high fever may start.
Measles can lead to other infections
About 30 percent of people with measles have serious issues due to the infection, says Daniel Kaswan, MD, an expert in infectious diseases at Aventura Hospital and Medical Center in Aventura, Florida.
The risk is greater for people:
- Under age 5
- Older than age 20
- Who are pregnant
- With weakened immune systems
Measles can lead to:
- Diarrhea
- Ear infection
- Pneumonia. This is an infection of the lungs. It is the most common cause of death in young children with measles.
Measles can weaken the immune system. That makes it harder for the body to fight off germs. Infection with bacteria is a common issue, says Dr. Kaswan.
Measles can cause serious issues
Young children who get measles may get viral croup. This causes the airways to swell up. They get narrow. It makes it hard to breathe. Signs are:
- Cough that sounds like barking
- Hoarse voice
- Noisy breathing
People with severe signs may need hospital care.
Measles can cause encephalitis, too. This affects the brain. About one in every 1,000 people with measles gets it. It can cause:
- Seizures
- Deafness
- Brain damage
Pregnant people who get measles are at greater risk for:
- Early birth
- Low-birth weight baby
- Miscarriage
Very rarely, measles can lead to subacute sclerosing panencephalitis (SSPE). This condition does not have a cure. It gets worse over time. It usually leads to death.
Children who were infected before age 2 can get SSPE many years later. It can happen seven to 10 years later.
SSPE affects the nerves. Some early signs are:
- Irritability
- Sleep issues
- Memory issues
Some later signs are muscle jerks and seizures. SSPE can lead to:
- Blindness
- Not able to swallow
- Not able to speak
- Death
Measles doesn’t boost immunity
Research suggests measles may actually weaken the immune system.
One study found measles may erase the immune system’s memory of other infections it has fought off. People may get infected with these germs again. The study was published in the journal Science in 2019.
Scientists have found that measles may erase 11 to 73 percent of the antibodies people have to other infections. It may take months to years for the immune system to recover. Your body makes antibodies. They help you fight off infections.
The MMR shot protects you
About 25 precent of people with measles will need hospital care. One or two out of 1000 will die.
One dose of the MMR shot is 93 percent effective against measles. Two doses are advised. Two doses are about 97 percent effective. For most people, this protection lasts for the rest of their life.
“The point is that measles is preventable,” Kaswan says. “So why expose yourself to any of this?”
When less people get the shot, measles spreads more easily. The virus lives in the nose and throat of people who are infected. It spreads through the air when they cough or sneeze. It can stay in the air or on surfaces for up to two hours. You can get infected if you touch a surface that has the virus on it. And then touch your eyes, nose, or mouth.
Up to 90 percent of people who have not had the MMR shot and are exposed to measles will get infected. People who are infected can spread measles for up to four days before showing signs.
Kaswan says people who have not had the MMR shot should get vaccinated within 72 hours of being exposed. A medicine called immunoglobulin (IG) can also be given. If you get it within six days of being exposed, it may protect you against measles. You may have milder signs if you do get sick.
You should contact your primary care doctor as soon as you can, Kaswan says. You can contact local health officials, too.
People with measles should avoid public places. They should stay home until their doctor says they can return to their typical routines.
About three out of 100 people who have had both MMR doses may become infected if they are exposed. Experts don’t know why. They say the MMR shot can still help. These people may have a milder illness. They will be less likely to spread the virus.
If you aren’t sure if you are immune, talk to your healthcare provider (HCP). Talk to them if you:
- Got the shot before 1968
- Are in college
- Work in healthcare
- Travel to other countries
Labs tests can check if you’re immune. It can cost more. It can take more time than getting a shot. Even if you’re immune, there is no harm in getting another dose.
Getting the MMR shot can protect you and those around you from measles.
