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

Background and aimsDespite the high national vaccination coverage, a large outbreak of mumps occurred 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.MethodsThe 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.ResultsMumps 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.ConclusionsLow immunity levels, combined with overcrowding and social mixing, were the main predisposing factors of the enhanced epidemic transmission of mumps in the ultraorthodox Jewish communities and further country-wide spread.