The U.S. is in the middle of the worst outbreak of measles since the disease was eradicated from the country in 2000. But while the majority of victims are children whose parents decided not to vaccinate them or people who have chosen to go unvaccinated, even some people who got the measles vaccine as children might still be at real risk, depending on their age.
Earlier this month, Israeli public health officials reported that a 43-year-old Israeli woman had fallen into a deep coma as a result of a measles infection, a rare complication of the viral, flu-like disease. Israel is currently struggling with its own outbreaks of measles, and like the one in the U.S., it’s largely due to transmission between pockets of unvaccinated people (the woman was a flight attendant on an airline that regularly flies between the U.S. and Israel, so she may have contracted it in either country). But the woman herself was vaccinated, though not to the same degree as many people are now.
Nowadays, children get two doses of the combination measles, mumps, and rubella, or MMR, vaccine starting at the age of one. But as recently as the 1980s, people in the U.S. and elsewhere were only given one shot. It was only in 1989, following a series of outbreaks, that public health experts in the U.S. endorsed a two-dose MMR schedule. The MMR vaccine, like so many, isn’t perfectly effective against measles even with two shots (97 percent effective), but it’s still better than one shot (93 effective).
That doesn’t necessarily mean everyone born before 1989 should immediately rush out and get vaccinated with MMR again. The Centers for Disease Control and Prevention only recommends, for instance, that people who were vaccinated between 1963 to 1967 with a killed virus vaccine get a shot of the current MMR vaccine, since that older version wasn’t very effective. The CDC also recommends that adults who are somehow still unvaccinated get at least one shot’s worth of protection.
That said, we do know that our vaccine-provided immunity to measles can wane years or decades later, even in people who have gotten two shots. And interestingly enough, research has also shown that growing outbreaks of mumps in young people may be tied to waning immunity at a much faster rate from the MMR vaccine, which has led to calls by some scientists for a routine third booster shot at age 18. Meanwhile, the CDC says public health officials can recommend a third booster for people at increased risk of mumps, such as those living near a current outbreak.
But what if you live in an area that’s currently experiencing a measles outbreak? From what we know, there’s little added benefit to getting a third MMR shot for measles alone. But if you’ve had only one MMR shot (or don’t know your vaccination history), there’s no real harm in going to the doctor and asking them about getting the vaccine, especially if you’re living in one of the five states (California, Michigan, New Jersey, New York, and Washington) where an outbreak is currently raging.
Indeed, at least on Twitter, vaccinated people, including doctors, have reported going to their physician to get their antibody levels tested, and in some cases getting a booster if those levels are particularly low.