Outbreaks of mumps among vaccinated adolescents and young adults

Filed under: Teens, Health & Safety: Babies, Nutrition: Health, Development/Milestones: Babies

Vaccines don't always work. That shouldn't come as any great surprise, but an article in the current issue of CMAJ reported before the widespread use of vaccines, mumps was the most common cause of viral meningitis (up to 10% of mumps infections). Vaccination programs, however, resulted in a drop of more than 99% in the number of reported mumps cases in the United States and Canada. Although rare in Canada, outbreaks have recently occurred throughout the world, including a large outbreak in the United Kingdom, where more than 56 000 cases were reported in 2004?2005.

Two recent outbreaks in Nova Scotia were investigated by public health officials. The first outbreak involved 13 high-school students (median age 14 yr): 9 who had previously received 2 doses of measles mumps rubella vaccine (MMR) and 4 who received a single dose. The second outbreak comprised 19 cases of mumps among students and some staff at a local university (median age 23 years), of whom 18 had received only 1 dose of MMR (the other received a second dose). The viruses identified in the outbreaks were phylogenetically similar and belonged to a genotype commonly reported in the UK. The virus from the second outbreak is identical to the strain currently circulating in the UK and United States.

The predominance in these outbreaks of infected people of university age not only highlights an environment with potential for increased transmission but also raises questions about the efficacy of the MMR vaccine. The people affected may represent a "lost cohort" who do not have immunity from natural mumps infection and were not offered a 2-dose schedule. Even with the possible failure of the vaccine, I'd still have my child immunized against the mumps. It is better than the specter of viral meningitis.

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Start by teaching him that it is safe to do so.