You’re not alone if you’re a bit freaked out about the outbreaks of measles that cropped up in New York in February and March, along with the March outbreak in Los Angeles. There’s valid reason to be concerned: “Measles is extremely contagious—think airborne, respiratory droplets,” explains Beth Ricanati, M.D., YouBeauty Wellness Expert. “While a healthy adult might be able to handle an exposure easily, [an infected person] could easily pass it along to a more susceptible individual, such as a small child or an elderly or immunocompromised individual.”On average, 90 percent of those exposed to someone infected with measles will contract the disease unless they’ve been vaccinated or had measles themselves in the past.The only way to protect yourself against infection is through vaccination with the measles, mumps, and rubella (MMR) vaccine. The first dose of the MMR vaccine is given at 12 to 15 months of age, while the second dose is recommended between four and six years of age.  People who receive the MMR vaccine will develop life-long immunity to all three viruses.Before these outbreaks, most people wouldn’t have given measles much thought. But it wasn’t that far in the past when the disease was a genuine problem in the U.S.  Before the measles vaccination program started in 1963, an estimated 3–4 million people in the United States were infected with measles each year, a whopping 90 percent of whom had measles by age 15, and up to 500 people died from the disease, according to the Centers for Disease Control and Prevention (CDC).The measles vaccine has reduced cases of the disease in the U.S. by more than 99 percent. In fact, the vaccination program was so successful that measles was declared eliminated—defined by an interruption of continuous transmission of infection lasting at least a year—in the United States in 2000.But with a subset of the population in the states choosing not to vaccinate their children, along with unvaccinated Americans—including families traveling with unvaccinated babies—who are importing measles to the U.S. after visiting countries with lower vaccination rates, it’s no surprise that the number of measles cases is rising here. During 2001–2012, the median annual number of measles cases reported in the U.S. was 60. Just during January 1–August 24, 2013 alone, there were a total of 159 cases of measles reported across 16 states in the U.S. Most cases—82 percent—were in people who were unvaccinated.“Interestingly, nine of the recently confirmed cases in New York involved children: seven were too young for the vaccine and two were in families who had chosen not to vaccinate their children,” notes Dr. Ricanati. “Vaccines protect! This data just supports that fact.”Notes the CDC: “ These outbreaks demonstrate that unvaccinated persons place themselves and their communities at risk for measles and that high vaccination coverage is important to prevent the spread of measles after importation.”For people who choose to not vaccinate their children, it may seem that the decision only affects their own kids, when, in fact, it can have catastrophic consequences on the health of others—particularly infants and young children. Measles is the most deadly of all childhood rash/fever illnesses, according to the CDC.This is why “herd immunity”—having the majority of the population immunized to leave little opportunity for a disease outbreak, which in turn protects those not eligible for certain vaccines such as infants and people with compromised immune systems—is so important: “Herd immunity is an amazing public health concept: basically, once a large percentage of a population is vaccinated against a particular illness, the whole community is protected from that illness over time,” explains Ricanati.So if you’ve already been vaccinated, how worried should you be right now? Not very, according to Ricanati. “If someone is vaccinated, then there is no reason to worry about transmission,” she says.The exception: If you were vaccinated before 1968 with an inactivated (killed) measles vaccine, you should be revaccinated with at least one dose of live attenuated measles vaccine. The killed measles vaccine, available in 1963-1967, was not effective.If you’re still stressing about it or aren’t sure of your vaccination status, ask your primary care physician to do a blood test that will measure your antibodies against measles to make sure you’re protected.