5 Measles Outbreak Answers, from a Cleveland Clinic Expert Doctor

Wednesday’s confirmation that an unvaccinated, school-aged Texas child had died from measles preceded Friday morning’s news that in addition to the known outbreaks in Texas and New Mexico, four more U.S. states were reporting active measles cases.

On Thursday, Terry Simpson, MD, revealed via his social media channels that measles vaccination still leaves a vaccinated individual with a 3% chance of contracting the virus from a carrier. “Measles is probably the most highly contagious virus that we know about it,” Dr. Simpson said. “It is spread through the air, it can be spread from 100 feet away.” National experts say the incubation period for measles is seven to 21 days, meaning it came take that long for symptoms to present after exposure, though the most common infections present within 11 to 12 days following exposure.

Experts have also reiterated the point that measles is more contagious than flu or Covid. If you’re concerned about the risk for yourself or for someone you care for, we talked to Dr. Anthony Leung, DO, an infectious disease specialist from the Cleveland Clinic, for answers to a few of the most pressing measles outbreak questions.

How contagious and dangerous is measles?

“Measles is highly contagious and causes flu-like illness with a characteristic rash with potential serious consequences,” Dr. Leung says.

Pointing to the virus’s basic reproduction number, Dr. Leung says each person infected with measles could then infect 12 to 18 other people. By comparison, Dr. Leung explains that the seasonal flu’s basic reproduction number is one to two, Covid anywhere from about two to eight, and chicken pox is 10 to 12.

Measles can have long-lasting effects after infection, as Dr. Leung says pneumonia complications happen in one of every 20 measles cases. “The brain is affected in about one in 1,000 cases of measles and can cause deafness and intellectual disability,” he says. Death also occurs in about three out of every 1,000 measles cases.

Do you need a measles vaccine booster?

The MMR vaccine, which is typically given in two doses during childhood, protects against three diseases: measles, mumps, and rubella. Mumps is a viral disease affecting salivary glands, causing painful swelling in the jaw, along with other symptoms. Rubella is also a viral disease and was declared eliminated in the U.S. in 2004, says the U.S. Centers for Disease Control and Prevention (CDC), though it is still possible for cases to come in from other countries.

Though many in the U.S. have likely already received the MMR vaccine, the introduction to vaccine boosters during the Covid pandemic now has some wondering if they need an MMR booster as well. But most adults who received two doses of MMR vaccine as children are “considered to have lifelong immunity,” Dr. Leung says. “Boosters aren’t routinely recommended for most adults who were fully vaccinated.”

Dr. Leung says the CDC uses the following criteria to determine whether an individual has “presumptive evidence” of measles immunity:

• Written documentation of one or more doses of a measles-containing vaccine administered on or after the first birthday for preschool-age children and adults not considered high risk
• Written documentation of two doses of measles-containing vaccine for school-age children and adults at high risk, including students at post-high school secondary educational institutions, healthcare personnel, and international travelers
• Laboratory evidence of immunity
• Laboratory confirmation of disease
• Birth before 1957

What if you or your children currently aren’t vaccinated?

A 2024 CDC report suggests vaccination rates in children have dropped in recent years. In kindergarten-age children nationwide, only 93% had state-required vaccinations during the 2022-2023 school year—and only 92.7% had the MMR vaccine.

“I would strongly encourage getting children fully vaccinated with the MMR vaccine as soon as possible,” Dr. Leung says. “For children who haven’t received any doses, starting the series now offers important protection. For those who have only had one dose, completing the series is recommended.”

The CDC also recommends any adults who don’t meet the above requirements for presumptive immunity should also receive at least one dose of the MMR vaccine.

How quickly does the MMR vaccine offer protection?

Similar to the Covid vaccines, the MMR vaccine begins to offer protection about two weeks after receiving it. Dr. Leung says it’s about 93% effective in preventing measles, mumps, and rubella after the first dose, then about 97% effective after two doses.

If someone is exposed to measles, there are two options for post-exposure propyhlaxis (PEP), per Dr. Leung. An MMR vaccination can be given within 72 hours of the initial measles exposure, or immunoglobulin (also known as antibodies) can be given within six days of exposure.

How to minimize your risk for getting measles

Dr. Leung offers a few key suggestions to keep yourself and your loved ones safe and healthy, especially during public health events like the current measles outbreak. He emphasizes routine wellness practices, such as proper handwashing, avoiding touching your face, and considering mask-wearing in crowded indoor areas.

In addition, he suggests verifying your vaccination status and checking with your family members too. Stay aware of locations with outbreaks and avoid them if possible, and “If you believe you’ve been exposed and are not immune, contact your healthcare provider promptly,” he says.

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