Mumps: Gone? Uh uh.

The mumps vaccine was introduced in the US in late 1967. In 1968 there were 185,691 cases reported. The incidence then fell precipitously, and fewer than 300 cases a year were reported in 2001-2003. The CDC was confident that mumps could be eliminated by 2010. But in 2006, the largest outbreak in 20 years occurred, starting in Iowa and mostly involving college students. By year’s end over 6,500 cases had been identified, of which 85 required hospitalization. It is likely that the virus arrived from Great Britain, where an identical strain had been circulating earlier. A study just reported (Kutty PK et al., J Infect Dis. 2010 Sept 1;202(5):667-74,) estimates the prevalence of adequate immunity in the college age population in the US at 90%. This sounds fine, but 90-92% immunity is required in our population to achieve the ‘herd immunity’ effect that prevents widespread communication of this highly infectious agent. And in some subpopulations the rate is even lower, setting us up for another outbreak. An accompanying editorial asks whether we all need a third dose of the combined measles, mumps, rubella vaccine, but the answer seems to be probably not. It is important to be vigilant; many parents think that mumps and other childhood diseases have been eradicated, but only about half of the world’s countries require immunization against mumps, and if you travel or receive foreign guests, you can be at risk.