What to Know About Measles


This story originally ran May 18, 2019, and was updated January 31, 2024.

Measles was declared eliminated in the United States in 2000, but every year, the country has documented cases of the disease.

“The number of susceptible people has increased because of people citing religious or personal objections to immunizations and therefore not immunizing their children, based on a misperception of the risks and benefits of vaccines,” says David J. Weber, MD, MPH, an infectious diseases expert at UNC Medical Center.

Here’s what you need to know about measles, the vaccine and how to protect yourself and your family.

1. Measles is extremely contagious.

“Measles is the most contagious disease we know,” Dr. Weber says. Up to 90 percent of people susceptible to measles will get it if they are exposed. The virus lives in the nose and throat mucus of an infected person, and it spreads through coughing and sneezing. The virus can live in the air for two hours after a person with measles leaves a room.

2. Measles can cause severe complications, some of them long-term.

Besides the illness caused by measles itself—fever, cough, runny nose, rash—people who get measles are at higher risk of secondary problems such as pneumonia, inner ear infections, croup and diarrhea. Young children can experience fever-related seizures, and about 1 in 1,000 cases results in encephalitis, which is inflammation of the brain. As much as a decade after infection, people who had measles can develop an autoimmune-like illness.

In the United States, the mortality rate for measles—1 or 2 deaths per 1,000 cases—is much lower than in many other countries, where measles remains a major killer. Before the vaccine, 3 million to 4 million Americans were infected each year, and as many as 500 of them died.

3. The measles vaccine is extremely effective when administered properly—and extremely safe.

People who received two doses of live, attenuated measles vaccine (delivered as a combination measles, mumps and rubella, or MMR, shot) are more than 99 percent protected.

Serious side effects from any vaccine are rare, Dr. Weber says. In fact, he has provided and supervised more than 100,000 doses of all types of vaccines to health care professionals who work at UNC Medical Center, and he has never seen a hospitalization or any permanent adverse effects. Some people who receive the MMR vaccine will have mild and temporary reactions such as a sore arm or a mild rash.

“The risk of not getting immunized is much higher than any risk of a vaccine,” Dr. Weber says.

4. Children should be vaccinated between ages 12 and 15 months and again between 4 and 6 years.

The vaccine is not given to babies earlier because the antibodies they received from their mother in utero may continue to provide protection up to a year outside the womb, and because the effectiveness of the vaccine in newborns is not as good. Babies who live in communities where there is an outbreak or those who travel abroad can get the vaccine early, between ages 6 and 12 months, but they’ll still need two more doses at the normal recommended times.

Dr. Weber recommends that parents of babies younger than 12 months talk to their child care providers about vaccination policies at their day care center or school to ensure that all older children and adults around their babies are vaccinated.

5. Protocol for administering the vaccine has changed over the decades.

Today’s effective version of the vaccine has been in use since 1968, so people who had two doses since then should be immune, Dr. Weber says. However, two doses have only been recommended since 1989.

People vaccinated between 1963 and 1968 might have received an inactivated vaccine that was later shown to be less effective, but less than a million people are thought to have received that particular shot, Dr. Weber says.

Those born before 1957 are considered immune because it is highly likely they had measles as a child, given the disease’s ubiquity in that era and how contagious it is.

6. Some people can’t receive the vaccine and rely on others to get vaccinated and keep the disease at bay.

Infants younger than 1, pregnant women and people who are immunocompromised because of treatments for cancer or other illnesses cannot receive the vaccine for measles. That’s why it’s so important for people who can be vaccinated to do so, for the safety of the community as a whole, Dr. Weber says.

7. People who are traveling internationally should take precautions against measles.

Measles is present in greater numbers in many foreign countries than it is in the U.S. Right now there are outbreaks in Japan, Israel and Ukraine. Dr. Weber advises people who will be traveling abroad to check the Centers for Disease Control and Prevention website for travel notices and to talk to their health care providers about precautions such as a booster shot, if necessary. People who were never vaccinated should receive the MMR shot before traveling.

8. Pregnant women who have been properly vaccinated do not need to worry about their babies in utero.

The mother’s antibodies will go through the placenta and protect the child. “If the mother is immune to measles, even if she is exposed to measles, the baby is perfectly protected,” Dr. Weber says. Plus, “measles is not a disease that causes congenital abnormalities” like varicella (chickenpox) or rubella can.

9. Measles causes cold-like symptoms days before its telltale rash.

Measles presents first with a cough, runny nose and conjunctivitis, often called pinkeye. People are contagious as many as four days before a rash appears, Dr. Weber says.

People who have been exposed to the measles virus who have not been vaccinated, or who have received only one dose, should receive the vaccine within 72 hours, Dr. Weber says. People who can’t receive the vaccine can receive immunoglobulin, a blood product, intravenously for up to six days, and this provides some protection against measles.

10. People with symptoms they think could be measles should call their doctor before going into a doctor’s office or hospital.

To prevent transmission, a clinic or hospital has procedures for safely bringing in a person who might have measles or another highly contagious disease, Dr. Weber says. This is likely to involve both the patient and all providers wearing masks and the patient being brought directly to a private room rather than waiting in a common area. At UNC Medical Center, there are “airborne isolation rooms” for this purpose; the air is exchanged frequently and sent directly outside rather than to other parts of the hospital, which reduces risk of airborne infection.

If you’re concerned about your immunity to measles, talk to your doctor. If you need a doctor for you or your child, find one near you.