Sero-prevalence of mumps antibodies in subpopulations subsequently affected: By a large scale mumps epidemic in Israel

Background and aims: Despite the high national vaccination coverage, a large outbreak ofmumpsoccurred in Israel, in 2009-2010, with onset and heavy transmission in ultraorthodox Jewish communities and further country-wide spread. We examined the sero-prevalence of mumps antibodies in the subpopulations subsequently affected by this large mumps outbreak, compared with the general population. Methods: The study was conducted in ultraorthodox Jewish communities, in Jerusalem district (N= 251), in Bnei Brak city in Tel Aviv district (N= 453), and in the general population (N= 1846), using residual sera of 1-20 year old subjects. Mumps IgG antibodies were measured using Enzygnost anti-parotitis virus IgG ELISA kit. Results: Mumps sero-positivity was significantly lower in Jerusalem: 51.8% (95% CI 51.9-61.0), and Bnei Brak: 56.5% (95% CI 45.6-57.9), than in the general population: 68.1% (95% CI 66.0-70.2). Sero-positivity increased with age, however in Jerusalem it was substantially low (46%) in the age group 10-20 years. This age group comprised a significant portion of mumps patients in the 2009-2010 outbreak. Conclusions: Low immunity levels, combined with overcrowding and social mixing, were the main predisposing factors of the enhanced epidemic transmission ofmumpsin the ultraorthodox Jewish communities and further country-wide spread.