A mumps outbreak among college students in 2006 made the CDC investigate who in America was the most immune to the virus. Their results indicate that those born before the vaccination was introduced and those people born outside of the United States have a higher resistance to the mumps than those who were born in the US within the last 30 years. Furthermore, despite traditionally lower vaccination rates when compared to whites, blacks had higher levels of protection than any other American-born race/ethnic group regardless of era. This was true for Mexicans born outside of the US as well, even though the mumps vaccine wasn't introduced to Mexico until 1998. In both cases, the CDC attributed this stronger immunity to a higher likelihood of natural exposure to infection, although strangely the researchers didn't actually ask anyone if they'd had the mumps OR if they'd ever been vaccinated against it. The authors called this a "limitation" of the study.
This study was performed by employees of the CDC and Sanofi Pasteur, "The largest company in the world devoted entirely to human vaccines." They looked into multiple factors, such as education, access to healthcare, health insurance, how many people lived in the same home, and income but only found significant differences between the 5 eras based on birth, race/ethnicity and country of birth (see graph). The MMR vaccine was introduced in 1967, and those born between 1967-1976 had the lowest levels of response (85.7) when their immune systems were tested against the virus. The groups born 1977-1986 and 1987-1998 had about the same level of response (90.1, 90.3 respectively) even though the youngest were the only generation to have the second MMR booster recommended by the CDC in 1989. Despite the policy's best intentions, the under-30's still weren't able to get back to the level of immunity of their baby-boom counterparts; those born between 1949-1956 reigned supreme with an average of 93.4, while their younger siblings born between 1957-66 came in at a slightly lower 2nd place.
White high school and college-aged kids had the highest infection rate in the 2006 outbreak and were found to have the lowest immunity among the 1977-86 and 1987-98 age groups. The authors attempted to explain why it was these kids, and not those born in the 1967-76 tier, who dominated the infections by hypothesizing that transmission of mumps happens in close quarters, like schools, college campuses, and the military. I don't think they really mean that blacks and hispanics don't go to school or serve in the military, or that these kids grew up without parents, but that's the impression their conclusions give. It's not the only ridiculous statement in here- they also attempt to explain why women had a higher infection rate than men, despite their higher level of immunity, by determining it was due to "differences in social behavior, with closer interpersonal contact among females..." Mumps travels in saliva and mucous. If there's one thing I know about high school and college aged boys, it's that they're full of both and not shy about sharing it with anyone. I don't know what kind of kissing parties these guys think are going on, but I think it was a bit of a reach.
As a side note, any recommendation for an additional booster that may come from this study should also be forced to disclose that, unlike measles and rubella, no antibody level has ever been established for mumps that defines whether or not someone will be protected from expressing the disease. Furthermore, the US has returned to pre-outbreak status with around 300 cases annually.
Preeta K. Kutty Deanna M. Kruszon‐Moran, Gustavo H. Dayan*, James P. Alexander, Nobia J. Williams, Philip E. Garcia, Carole J. Hickman, Geraldine M. McQuillan, and William. J. Bellini (2010). "Seroprevalence of Antibody to Mumps Virus in the US Population, 1999–2004." The Journal of Infectious Diseases 202: pp 667–674. DOI: 10.1086/655394.
*Employed by Sanofi Pasteur
