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What L.A.'s Mumps Outbreak Tells Us About Our Vaccine Policies

Kids need to be vaccinated and adult travelers need booster shots.

Los Angeles County has been suffering a mumps outbreak since the beginning of the year, with more than 40 Angelenos falling sick.

Most cases of mumps aren't dangerous—people may get a fever, fatigue, and swelling in their salivary glands. But in rare cases, mumps can cause testicular swelling and infertility in men, and complicate pregnancies. The Los Angeles County public-health department sent out a note late last week asking doctors to tell their patients who might be infected to stay away from public spaces, and to report cases to their local health department. (There's no mandatory rule to report mumps.) Mumps spreads in close quarters, such as gyms or bars. While the M.M.R. immunization, which most Americans get as children, protects against mumps, its effects tend to fade once people hit their 30s and 40s.

Unlike other recent outbreaks of vaccine-preventable diseases—such as the rash of measles among Somali Americans in Minnesota, who had been told by activists that vaccines cause autism, which is untrue—L.A.'s mumps cases aren't directly attributable to the anti-vaccine movement. The affected in this case are adults, not children whose parents have refused vaccinations, and the United States' adult vaccination rate is high. In addition, it's not clear whether mumps has become more common in America since anti-vaccine activists gained traction. It might be that new tools for diagnosing mumps have made identifying the disease easier, says Jeffrey Klausner, a doctor who studies infectious diseases at the University of California–Los Angeles. (In contrast, measles in the U.S. is clearly on the rise because of pockets of parents who don't immunize their children.)

Still, L.A.'s mumps outbreak points to some public-health needs, Klausner says.

Americans are traveling internationally much more than they did 20 years ago, and they might be bringing mumps into the U.S. from destinations where immunization rates are low. "When people are going on a trip, it's important to make sure that their routine vaccinations, like measles, mumps, and rubella, are up to date," he says. Adults can get a booster shot before heading abroad.

Children should also continue to be vaccinated on time, as it's clear vaccine-preventable illnesses are still circulating. California's kindergartner immunization rates, which had been falling since the anti-vaccine movement was founded in the late '90s, started shooting back up after a big measles outbreak in Disneyland prompted the state to pass a stricter law against school immunization exemptions.

Klausner has an unique idea for preventing outbreaks in the future: He wants to see more doctors report to the state's vaccine registry, which is voluntary. If they did, any Californian who walks into her local CVS or Walgreens that offers booster shots could have the pharmacist check she's up to date. She can then fill in what's missing right there. "It's achievable, but we haven't really seen the political will to make that happen," he says.