(NEXSTAR) -- More than 250 cases of measles have been reported in the U.S., nearly all of which have been associated with three outbreaks, according to the Centers for Disease Control and Prevention. In light of the rise in cases, the CDC has warned that everyone "should be up to date" on their vaccinations.
But how do you know if you are? And how do you know if it's time to get a booster?
Most have likely already been vaccinated against measles.
The current CDC vaccination recommendations say children should receive two doses of the MMR (measles, mumps, and rubella) vaccine: the first when they're between the ages of 1 year and 15 months, and the second when they are between the ages of 4 and 6 years old but before they start school. If a child is receiving the MMRV (measles, mumps, rubella, and varicella) vaccine, the second dose can be given three months after the first dose up until they turn 12. The first dose, according to CDC recommendations, should be separate MMR and varicella vaccines.
Some people may have presumptive evidence of immunity if they were born before 1957 or have laboratory evidence or confirmation of immunity or disease.
Do you need a measles booster?
Those who live in areas experiencing measles outbreaks, are at high risk for infection, and received the vaccine many years ago may want to consider getting a booster, said Scott Weaver with the Global Virus Network, an international coalition.
If you are considered to have immunity, either with the vaccine or an accepted piece of presumptive evidence, you may not need a booster, according to Dr. Scott Roberts, a Yale Medicine infectious diseases specialist.
You may want to seek out another dose if you received the vaccine before 1968, Dr. Alex Dresden of SSM Health says, "as the newer one is more effective."
It is recommended that anyone who has not received a vaccine and never had measles get at least one MMR shot, Roberts explains. If you fall into this category and are also at a high risk for exposure -- because you are a student in a post-secondary institution, are a health care worker, travel internationally, or may become pregnant -- a second dose is suggested at least 28 days after the first, he adds.
If you fall into any of those groups, or have concerns about measles, it's recommended that you speak with your healthcare provider. Getting another MMR shot is harmless if there are concerns about waning immunity, the CDC says.
What is measles?
Measles is an airborne and extremely infectious illness known for causing a potentially severe rash. While not seasonal, cases have spread when there is increased travel or unvaccinated people in close quarters, like summer camps, according to the CDC.
Before the vaccine was available, roughly 48,000 people in the U.S. would be hospitalized for measles annually, the CDC says, with hundreds dying. Now, two doses of the MMR vaccine (the standard amount recommended in the U.S.) have been found to be 97% effective at preventing measles. A single dose is 93% effective, according to the CDC.
The U.S. determined measles had been eliminated in 2000 because of high vaccination rates, but those have been slipping in recent years. Fewer than 95% of kindergartners are up to date on their MMR vaccines, with rates continuing to drop. CDC data shows that in only 11 states -- California, New Mexico, Mississippi, Tennessee, West Virginia, Maryland, New York, Connecticut, Rhode Island, Massachusetts, and Maine -- was the kindergarten vaccine coverage at 95% or higher in 2024.
Meanwhile, fewer than 90% of young children in 15 states -- Alaska, Hawaii, Idaho, Utah, Colorado, Oklahoma, Minnesota, Iowa, Wisconsin, Georgia, Florida, Ohio, and New Hampshire -- are vaccinated.
What's the latest on the 2025 measles outbreak?
Most of this year's cases have been reported in Texas. As of Tuesday, state health officials reported 223 cases. Twenty-nine people in the state are hospitalized. Neighboring New Mexico reported three additional cases, bringing the state total to 33.
Deaths have occurred in both states -- in Texas, a school-age child died last month while New Mexico reported its first adult death last week.
Oklahoma's state health department reported two probable cases of measles Tuesday, saying they are "associated" with the West Texas and New Mexico outbreaks.
Measles cases have been reported in Alaska, California, Georgia, Kentucky, Maryland, New Jersey, New York, Pennsylvania and Rhode Island.
There's no specific treatment for measles, so doctors generally try to alleviate symptoms, prevent complications and keep patients comfortable.