Do I Need a Measles Booster Shot and How Do I Protect My Family?

• Amid the measles outbreak expected to “expand rapidly,” people are confused about whether they need a booster
• Anyone who has had two shots of the MMR vaccine, which protects against the virus, is considered “immune for life,” an expert tells PEOPLE
• If you’re not sure of your vaccination status, consult with your doctor to discuss next steps

The measles outbreak in the Southwest continues to spread, and “more cases are expected,” U.S. Centers for Disease Control said, as “this outbreak continues to expand rapidly.” Cases have now been documented across the U.S., in nearby Oklahoma, as well as New York, New Jersey and Alaska. 

The outbreak has resulted in the deaths of three people, including a child who was not vaccinated according to the Texas Department of State Health Services. Compared to 2024 when there were 285 cases total, the CDC said there are already 301 confirmed cases in the first three months of 2025.

According to the CDC, the best safeguard against measles is “two doses of the MMR vaccine” — which protects against measles, mumps and rubella. The first dose is administered between 12 and 15 months of age; the second shot comes between 4 and 6 years. However, some adults may not remember getting the shots — or if they were born before 1957, traditional guidelines considered them immune. Measles was so widespread before the vaccine’s introduction in 1963, medical professionals assume most people were exposed to it, resulting in some immunity.

To address confusion surrounding whether people need further protection, PEOPLE spoke to Dr. Matthew Harris, pediatric emergency medicine physician and medical director for clinical preparedness for Northwell Health in New York.

Do I Need a Measles Booster?

“If you’ve been able to see from your childhood vaccinations that you’ve received two doses of the vaccine,” Dr. Harris tells PEOPLE, “you’re considered immune for life and there is no reason to get a booster.”

What If I Don’t Know My Immunization Status from Childhood?

“If you don’t know your status, I think it’s a worthwhile conversation to have with your practitioner,” Dr. Harris says, especially “if you came from somewhere that wasn’t a highly vaccinated population.” If your doctor advises it, “you can restart the series of the measles vaccine,” he says.

Is There a Way to Test for Antibodies?

Yes. If you are unsure whether you’ve had the two doses of the vaccine, a blood test can show whether you have titers, or antibodies. There is a measles-specific antibody.

“If you have the titer called IgG,” Dr. Harris explains, “then you can rest assured that you know you are protected against measles.”

Sometimes IgC may not show up in a fully vaccinated person, due to how long ago they were vaccinated, individual immune response or other reasons. “If someone’s fully vaccinated, even if you do not have high levels of titers, [you’ll have] another form of immunity called cellular immunity, which is just not something you can detect in a blood test.”

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You don’t need a titers test if you know you have been fully vaccinated, but it could be an option for someone who is not sure, so check with your doctor.

Can Anyone Get Vaccinated?

“For the most part, almost everyone can get vaccinated,” Dr. Harris adds. Few exceptions include pregnant people, patients undergoing chemotherapy or “patients who have certain immunologic diseases that might prohibit them from getting vaccinated.”

People Who Are at High Risk of Bad Outcomes — Like Those with Leukemia or HIV — May Be Worried About Exposure. What Should They Do?

“If you were born after 1957 and you think your parents gave you your shots as a child and you’re a healthy person, you do not need to rush off to get a booster,” Dr. Harris tells PEOPLE. “The likelihood is you’re vaccinated and protected.” But, he adds, “If you’re not sure, discuss it with your provider and if you’re a higher-risk patient, again you can consider getting titers [checked] as part of the discussion, but recognize that that information is imperfect.”

What Should I Do If My Child Is Too Young to Be Vaccinated?

“Understanding the vaccine practices at your daycare or in your community would be important, especially given the prevalence of cases,” Dr. Harris says. “I think parents have the information available to them to make an informed decision about how to keep their children safe. I want to be clear: I’m not recommending anyone staying home from daycare or school. It’s just that parents make informed decisions.”

Will There Be a Vaccine Shortage?

“There is a national shortage of the vaccine right now, but that’s not because of the measles; that has to do with one of the companies having a production problem,” Harris tells PEOPLE. “That’s another reason not to get an ‘unnecessary’ booster because if you are considered immune, you don’t need that booster, that should be reserved for children [who have] not yet been vaccinated.”

And while he says, “you will see some public health efforts” to vaccinate,“ they will be “nothing akin to what we saw with COVID.”