This study proves that mumps outbreaks still occur in highly vaccinated populations, indicating that the current vaccination program is ineffective in preventing mumps outbreaks.

PMID: 

J Virol. 2012 Jan ;86(1):615-20. Epub 2011 Nov 9. PMID: 22072778

Abstract Title: 

Recent mumps outbreaks in vaccinated populations: no evidence of immune escape.

Abstract: 

Recently, numerous large-scale mumps outbreaks have occurred in vaccinated populations. Clinical isolates sequenced from these outbreaks have invariably been of genotypes distinct from those of vaccine viruses, raising concern that certain mumps virus strains may escape vaccine-induced immunity. To investigate this concern, sera obtained from children 6 weeks after receipt of measles, mumps, and rubella (MMR) vaccine were tested for the ability to neutralize a carefully selected group of genetically diverse mumps virus strains. Although the geometric mean neutralizing antibody titer of the sera was lower against some virus strains than others, all viruses were readily neutralized, arguing against immune escape.

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