CNN
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Measles cases are popping up across the country, especially in areas with lower vaccination rates.
There were 285 cases reported in the US last year, the most since 2019, according to the US Centers for Disease Control and Prevention. And cases have already emerged in 2025: Two cases of measles were detected in metro Atlanta last week; this week, one case was confirmed in New Mexico, and an outbreak in West Texas is growing, with 24 cases, according to the state health department. Cases have also been identified in Alaska, Rhode Island and New York City.
Measles is a highly contagious airborne illness that can cause rash, fever, red eyes and cough. Severe cases can result in blindness, pneumonia or encephalitis, swelling of the brain according to the World Health Organization. In some cases, the illness can be fatal.
Prior to the introduction of the measles vaccine in 1963, the virus would claim an estimated 2.6 million lives each year worldwide. In 2023, WHO estimated that there were 107,500 measles deaths, largely in countries with low vaccination.
“We’ve eliminated the memory of measles. I don’t think people remember how sick that can make you,” said Dr. Paul Offit, director of the Vaccine Education Program at the Children’s Hospital of Philadelphia.
Experts say it’s a good time for everyone to be thinking about their immunity to measles.
The best way to stay protected against measles is to get vaccinated, according to experts. The measles, mumps and rubella (MMR) vaccine is 93% effective against measles after one dose and 97% effective against measles after two, according to the CDC.
Officials’ guidance says children should get two doses of the MMR vaccine: the first dose between 12 and 15 months and the second around age 4, before starting school.
“When people consider their choice about vaccinating their child, it isn’t just about their own individual child, but this is a public health issue. … If we just stop thinking about the health of the population, we are going to see more and more vaccine-preventable illness, outbreaks occur,” said Dr. Christina Johns, a pediatric emergency physician at PM Pediatrics.
Older children or adults can also get vaccinated if they didn’t get the vaccine as a child, she says. However, people born before 1957 are likely to have been naturally infected and thus already have immunity, according to the CDC.
CDC guidance also indicates that if someone is exposed to measles, getting the MMR vaccine within 72 hours could induce some protection or result in less serious illness.
Across the country, cases are rising now in large part due to declining vaccination rates, which Johns said stems from “the misinformation and disinformation campaigns that have gone wild and run rampant.”
A record share of US kindergartners had an exemption for required vaccinations last school year, leaving more than 125,000 new schoolchildren without coverage for at least one state-mandated vaccine, according to data published by the CDC in October.
The US Department of Health and Human Services has set a goal that at least 95% of children in kindergarten will have gotten two doses of the MMR vaccine, a threshold necessary to help prevent outbreaks of the highly contagious disease. The US has now fallen short of that threshold for four years in a row.
Titer tests at a primary-care office can be used to check for immunity against measles. Some doctors say that this is not necessary, though, if you have gotten both recommended doses of the MMR vaccine or have had the measles itself.
Titer tests can detect the presence of antibodies – infection fighting proteins produced by immune cells in response to a specific foreign pathogen – at high concentrations. When you have an infection or you get vaccinated, your immune cells learn how to produce antibodies against the virus and can stay in your system for years, helping fight repeat or future infections.
In the case of measles, a virus with a longer incubation period, the body has longer to prepare to fight the infection, including more time to produce antibodies. So even if the titer tests don’t show high levels of antibodies, your immune memory cells may still be able to respond to the virus quickly, according to Offit.
“All you need is memory,” he said. “It’s not likely tested in a commercial laboratory.”
The commercial laboratory tests or titer tests are most useful for people who don’t know their vaccination status, experts say.
This happens “particularly if they don’t have access to their own vaccination records, which is so often the case because people move, pediatric practices go – the pediatrician passes away or retires and you can’t contact the office anymore,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center.
Doctors may also want to test people who have weakened immune systems to see how much immunity they have to measles. In this case, immunosuppressed patients may not be eligible for the vaccine, which uses live but weakened form of the virus, but they may want information about their immunity status and to discuss further with providers.
If you were vaccinated with the first version of the measles vaccine – a killed-virus vaccine used between 1963 and 1968 – or don’t know which type of vaccine you received, the CDC recommends getting at least one dose of MMR.
Experts say that those who received two doses of the current MMR vaccine will probably have measles immunity for their entire life.
“Less than 1% of people who are fully vaccinated will have waning immunity to measles to the point where they are susceptible to infection,” Johns said. “As we age, all types of immunity have the potential to wane, but fully vaccinated folks are generally considered protected from infection for their lifetime.”
During mumps outbreaks, it is possible that local authorities may recommend additional MMR doses for those who are at risk of heavy exposure, according to the CDC.
For measles, Schaffner says some people may find that they have low titers of antibodies after testing and, “in conjunction with their physicians, decide to get another dose of the vaccine booster. And I’d say there’s no harm to that as far as we know, but the benefit is uncertain.”