Abstract
BackgroundMumps is a vaccine-preventable disease but outbreaks have been reported in persons vaccinated with two doses of MMR vaccine.The objective was to describe the demographic features, vaccination effectiveness and genetic mumps virus diversity among laboratory-confirmed cases between 2007 and 2011 in Catalonia.MethodsCases and outbreaks of mumps notified to the notifiable diseases system of Catalonia between 2007 and 2011 retrospectively registered were included. Public health care centres provided written immunization records to regional public health staff to determine the vaccination history.Saliva and serum specimens were collected from suspected cases for laboratory-confirmation using real-time reverse-transcriptase PCR (rtRT-PCR) or serological testing.Phylogenetic analysis of the complete SH gene (316 nucleotides) and complete coding HN protein (1749 nucleotides) sequences was made.Categorical variables were compared using the Chi-square or Fisher’s tests and continuous variables using the Student test. Vaccination effectiveness by number of MMR doses was estimated using the screening method.ResultsDuring the study period, 581 confirmed cases of mumps were notified (incidence rate 1.6 cases/100,000 persons-year), of which 60% were male. Three hundred sixty-four laboratory-confirmed cases were reported, of which 44% were confirmed by rtRT-PCR. Of the 289 laboratory-confirmed cases belonging to vaccination cohorts, 33.5% (97) had received one dose of MMR vaccine and 50% (145) two doses.Based on phylogenetic analyses of 316-nucleotide and 174-nucleotide SH sequences, the viruses belonging to viral genotypes were: genotype G (126), genotype D (23), genotype H (2), genotype F (2), genotype J (1), while one remained uncharacterized.Amino acid differences were detected between circulating strains and the Jeryl Lynn vaccine strains, although the majority of amino acid substitutions were genotype-specific.Fifty-one outbreaks were notified that included 324 confirmed mumps cases. Genotype G was the most frequent genotype detected. The family (35%), secondary schools (25%) and community outbreaks (18%) were the most frequent settings.ConclusionsOur study shows that genotype G viruses are the most prevalent in Catalonia. Most cases occurred in people who had received two doses of MMR, suggesting inadequate effectiveness of the Jeryl Lynn vaccine strain. The possible factors related are discussed.
Highlights
Mumps is a vaccine-preventable disease but outbreaks have been reported in persons vaccinated with two doses of mumps and rubella vaccine (MMR) vaccine
Most cases occurred in people who had received two doses of MMR, suggesting inadequate effectiveness of the Jeryl Lynn vaccine strain
Vaccination status and vaccine effectiveness Of the 364 laboratory-confirmed cases, 297 (81.6%) had criteria for MMR vaccination as they were born after 1980, when the childhood immunization schedule was introduced in Catalonia
Summary
Mumps is a vaccine-preventable disease but outbreaks have been reported in persons vaccinated with two doses of MMR vaccine. The objective was to describe the demographic features, vaccination effectiveness and genetic mumps virus diversity among laboratory-confirmed cases between 2007 and 2011 in Catalonia. Mumps infection may result in clinical complications including aseptic meningitis, encephalitis and orchitis, among others. Laboratory confirmation is based on the detection of MuV-specific immunoglobulin M (IgM) antibodies in serum or saliva specimens, by viral isolation in cell culture, or by detection of viral genomic RNA in clinical samples using molecular methods. Up to 12 genotypes (A to N, excluding E and M) are currently recognised based on sequence analysis of the entire 316 nucleotides of the small hydrophobic (SH) gene, including the non-coding regions flanking the coding sequence of the SH protein [2]. The WHO recommends MuV genotyping as a tool for the distribution of the genetic lineages that co-circulate worldwide and for viral epidemiological surveillance to trace the patterns of virus spread
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