Measles, a highly infectious and preventable disease considered eliminated in the U.S. a quarter century ago, is now spreading in at least two states. Here are some answers to common questions about the disease, from how it presents to the durability of vaccinations.
Q: What is measles and why are we hearing about it now?
A: The World Health Organization identifies measles as one of the most contagious diseases, killing up to three out of every thousand children globally. The disease has been preventable since 1963, when American researchers developed a vaccine. In 2000, measles was considered eliminated in the U.S., though occasional cases and outbreaks impacted mostly unvaccinated people. Currently, there are outbreaks in Texas and New Mexico.
On March 6, an unvaccinated man in New Mexico died of measles. An unvaccinated school-aged child in West Texas died of the virus last month.
The Texas state health department reports that 90% of non-immune people become infected just by being near someone with the airborne sickness. The rubeola virus that causes measles can linger in midair for up to two hours.
Q: What are the symptoms of measles and when do they appear?
A: The Centers for Disease Control and Prevention says that measles symptoms — fevers of 104 degrees Fahrenheit or above, cough, runny nose, and red, watery eyes — appear within 14 days after an infection. Next come tiny white “Koplik spots” on the inside of the mouth, and a rash that starts at the hairline and spreads down the body.
Medical complications can include pneumonia, deafness, blindness, encephalitis (brain swelling) and subacute sclerosing panencephalitis, a progressive neurological disease. Children 5 and under, adults over 20, pregnant women, and immunocompromised people such as chemotherapy patients and those living with leukemia or HIV are most vulnerable to complications.
Q: What are the vaccine requirements?
A: Federal requirements for Measles, Mumps, and Rubella (MMR) shots don’t exist, but all 50 states enforce some form of measles inoculation for children before they enter childcare or public schools. Some states, such as Texas, allow vaccination exemptions for religious and personal beliefs. California had a similar exemption until it was eliminated in 2016.
A CDC-recommended measles vaccination includes two shots delivered at 12-15 months and 4-6 years of age. Together, the doses are 97% effective against measles infections. By contrast, unvaccinated people represent about 94% of the 222 measles cases in the U.S. this year, and one in five unvaccinated people with measles requires hospitalization.
But these statistics have not deterred a persistent anti-vaccination movement that expanded during the COVID-19 pandemic. Lawmakers in Texas and numerous other states continue pushing bills to dislodge routine vaccination from public health policy.
A February meeting of the CDC’s Advisory Committee on Immunization Practices has been indefinitely postponed and U.S. Health Secretary Robert F. Kennedy Jr. is stoking skepticism and confusion around vaccines.
Q: If I got vaccinated as recommended, am I OK? Isn’t the MMR vaccine good for life?
A: MMR vaccinations or natural immunity after a measles infection theoretically lasts a lifetime, according to Dr. Monica Gandhi an infectious disease doctor at UC San Francisco.
But Gandhi said there has been no way to test this in the absence of the disease. “We haven’t put an 80-year-old in the situation where they’re in the middle of an outbreak in 2025,” she said.
Q: Should older vaccinated adults, and those born before 1957 and presumed immune from the widespread infections of the pre-vaccination era, get another MMR vaccine?
A: Gandhi said those vaccinated decades ago should consider a measles booster if they live near an outbreak, are 65 or older, or are preparing to travel internationally, especially for the first time.
The Yale School of Medicine recommends that at-risk people vaccinated prior to 1968 (57 or older) might also want a new shot, because they received doses that are less effective than vaccines that became the standard after that year.
Q: Should people who work in childcare or early education get boosters?
A: This depends on local risk levels, Gandhi said. Vaccination rates at more kindergartens have been dipping below the 95% level previously recommended (and in California, currently enforced) for herd immunity.
Q: Can children be vaccinated ahead of schedule, and can the gap between the two doses be shorter?
A: In the event of an outbreak, Gandhi said, the first dose can be given to infants under a year old. They must be re-vaccinated on or after their first birthdays with two more doses of MMR vaccine separated by 28 days or more, or two more doses of the measles-mumps-rubella-varicella (MMRV) vaccine separated by 3 months or more. The CDC has additional guidance for infants traveling internationally.
Q: Is there anyone for whom vaccination is unsafe?
A: Severely immunocompromised people and pregnant women should not receive the live vaccine, Gandhi said. If exposed to measles, this population receives immunoglobulins — protein antibodies that help the immune system fight off harmful agents.
Q: Kennedy has been touting vitamin A and cod liver oil as alternatives to combating measles. Scientists have debunked these suggestions, but is there any credence to claims that vitamin A or other nutrients can help reduce susceptibility to severe measles?
A: “I really want to downplay vitamin A as a treatment. Prevention by vaccination is the best way to combat severe measles,” Gandhi said.
“Two deaths in this country over the last month are a very big deal for a preventable infectious disease,” she said. “It’s a very big deal to lose someone in your family — it’s a lifelong tragedy. There’s simply no reason not to get the vaccine.”