Researchers at the US Center for Disease Control investigating a large outbreak of mumps in 2006, when 6,584 cases were reported among college students, have discovered that virtually every sufferer had been vaccinated twice against the disease.
The research reveals that at least 84% of young adults aged 18 to 24 years had received two-dose vaccines against mumps. And in 2006 – when the outbreak occurred – the national two-dose coverage among adolescents reached 87%, the highest in US history, and just one point below that needed for ‘herd immunity’.
CDC researchers speculate that the outbreak – primarily among 18 to 24-year-olds – was the result of the ‘wrong type of mumps’. The vaccine is supposed to protect against A-virus mumps, whereas the outbreak in 2006 was caused by the G-virus strain.
Despite its limitations, the CDC team reckons that all children need a third dose of MMR – even though the two-dose vaccine was introduced following a 1980 mumps outbreak among children who had received a single dose.
Source: New England Journal of Medicine, 2008; 358: 1580-9
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First Published in June 2008
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