Measles outbreaks in Texas and New Mexico are fueling concerns about the rapid spread of the highly contagious virus.
There have been more than 100 measles cases in the United States so far this year, compared to 285 cases in all of 2024. And health officials have warned that they expect more people to fall ill.
The outbreaks come as the rate of childhood vaccinations, including against measles, have fallen. Most of the measles cases in recent outbreaks have been among people who were unvaccinated or whose vaccination status was unknown. Many have been young children, who are at particularly high risk. An unvaccinated child died in Texas from measles, health officials reported Wednesday.
Vaccines are the most effective tools to combat measles. Breakthrough cases — infections among the vaccinated — are extremely rare. But as outbreaks spread, it’s important to review your own vaccination status and make sure you are properly protected.
How to check if you have immunity
More than 90 percent of children in the U.S. have received at least one dose of the shot that protects against measles, mumps and rubella, which is part of the routine child vaccination schedule.
If you are fully vaccinated — meaning you have received two doses at some point in your life — you should be set. Even though immunity from any vaccine wanes over time, the measles vaccine offers strong lifetime protection against infection for almost everyone, said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center.
The Centers for Disease Control and Prevention say that anyone born before 1957 is most likely protected from the virus, because measles circulated so widely then.
But if you were born afterward and are not entirely sure whether you were vaccinated, try to track down your medical records. You can also ask a doctor for a blood test to measure the amount of antibodies against measles in your blood.
Who needs another shot?
If you’ve received two shots
Even for people who live in an area where an outbreak is occurring, health officials generally do not recommend a booster or an extra dose of the vaccine.
“If someone has had two doses of the vaccine, there’s no reason for them to worry about it, or even think about getting a booster,” said Dr. Amesh Adalja, an infectious disease physician and senior scholar at the Johns Hopkins Center for Health Security. An exception is some people who have become immunosupressed since they were vaccinated, such as bone marrow transplant patients, he said; they may need to be revaccinated.
If you’ve only received one shot
If you were vaccinated before 1968, you may need at least one more dose, because the shot offered previously was less effective.
If you were vaccinated between 1968 and 1989, there may be some gap in immunity: During that time the C.D.C. recommended only one shot. A single dose is around 93 percent effective against measles. Now, the agency says full protection is two shots, which are roughly 97 percent effective.
If you have only had one shot, you should talk with a health care provider about next steps, said Robert Bednarczyk, an associate professor of global health at Emory University.
Most people who have had one dose do not need to seek out another, Dr. Adalja said. “One dose is pretty effective,” though he added that there’s no harm in getting another dose.
That said, there are specific situations in which you might want to consider getting a second dose if you’ve only had one shot, such as if you’re traveling anywhere outside of the country. Many popular international travel destinations have either greater rates of measles or lower vaccination rates than the United States, Dr. Bednarczyk said.
The C.D.C. recommends that school-aged children, health care workers, college students and some people with H.I.V. seek a second shot. The agency also advises family members and close contacts of people with compromised immune systems to receive two doses. During an outbreak, public health officials may recommend certain groups who are at increased risk for contracting the virus get a second shot.
Some people most at risk from the virus are not routinely vaccinated, like children under one year, pregnant women who have not received the shots and some people who are immunocompromised. That’s why vaccination rates in a community are so critical.
“Measles is one of the most contagious diseases that we know of,” Dr. Bednarczyk said. “So even when those coverage levels drop or the population level immunity drops a little bit, that’s where we can start to see larger outbreaks.”