Mumps Moves Back to Center Stage

Long after most of us thought that mumps had been banished to the sidelines by widespread childhood vaccinations, we are suddenly confronted with the largest outbreak in this country in two decades. In Iowa, the center of the widening epidemic, 975 cases have been reported since December, and more than 350 cases have been found in seven other states. The outbreaks will almost certainly get worse as college students and other young people, a key focus of infection, move around the country spreading their germs.

There was a time some decades ago when virtually all Americans came down with the mumps at a young age, a rite of childhood that gave them lifelong immunity. Then effective vaccines largely eliminated big outbreaks, driving the national caseload down to an average of 265 in recent years.

Mumps is not usually a very serious illness. Some people are not even aware they have the virus. Others develop such symptoms as fevers, headaches, fatigue and the telltale swollen saliva glands, which run their course within nine days.

But in rare cases there can be very serious complications, including meningitis, deafness, spontaneous abortion and an inflammation of the testicles that can lead to sterility.

The striking thing about the Iowa epidemic is that it is affecting mainly relatively young and healthy people, a vast majority of whom have been vaccinated at least once with a mumps-containing vaccine, and usually twice. Federal health officials say there is no reason to suspect any problems with the vaccine. Previous experience has shown that a single dose protects about 80 percent of the recipients and a double dose about 90 percent. That leaves at least 10 percent still vulnerable to infection, even if everything works as advertised. Throw in the small percentage of people who have not been vaccinated at all, and there are plenty of people to sustain an outbreak.

Even so, federal and state health officials will need to look hard for any signs that the mumps vaccine is less effective than we previously thought or that its effectiveness diminishes over time. Health officials are wisely urging students and others who are at high risk of exposure and are not fully immunized to get their shots. The current outbreaks would no doubt be much larger hitting thousands or tens of thousands of people without the high levels of vaccination already prevalent.