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The particularities of epidemic process in mumps and perfection of the surveillance


Author: Caterinciuc Natalia
Degree:doctor of medicine
Speciality: 14.00.30 - Epidemiology
Year:2009
Scientific adviser: Victoria Bucov
doctor habilitat, professor, National Center of Public Health
Scientific consultant: Constantin Andriuţă
doctor habilitat, professor, State University of Medicine and Pharmacy "Nicolae Testemitanu"
Institution:
Scientific council:

Status

The thesis was presented on the 26 August, 2009
Approved by NCAA on the 5 November, 2009

Abstract

Adobe PDF document0.36 Mb / in romanian

Keywords

mumps, epidemic process, surveillance, immunization campaign, immunization coverage, postvaccination immunity, laboratory examination

Summary

The aim of this work is – optimization of surveillance in mumps on the base of determination particularities of epidemic process, examination of postvaccination population's immunity and mumps cases' specific antibodies, the evaluation of mumps vaccination efficacy.

Specific comparative analysis of mumps morbidity in prevaccination and vaccination era has shown that due the systematic vaccination morbidity was important decreased with the middle annual rate of reduction equal to 6,2%, the middle annual incidence in vaccination era was 97,740/0000 comparing with 226,20/0000 in previously period. During the vaccination period modification in seasonality was observed and it was a little evident, was changed the urban-rural distribution of mumps morbidity and in both areas the level of incidence became identical, the tendency of maturization of mumps morbidity was observed.

Because of vaccine shortage and lack surveillance the mumps epidemics occurred in 1996-1998 and 2007-2008. During the last epidemics the highest number of mumps cases were in men, in organized collectives of children and young adults. In total were registered 30 633 cases of mumps, the incidence was 745,30/0000. The most affected ages were 15-24 years – 79,6% from total number of cases, including the persons of 15-17 years – 40,4%, the intensive index for 15-17 years was 6 082,20/0000, for 18-19 years – 4323,60/0000.

The data of serological examination with ELISA the level of specific mumps IgG antibodies showed that the group of the high risk were persons vaccinated once, the birth cohorts before 1994. During the population study was demonstrated that attack rate for once vaccinated persons was 28,2%, for vaccinated twice - 4,6%. For persons vaccinated once odds ratio increased with the ages, the risk factors for mumps were the next – contact with mumps cases, utilization of public transport once a week, living in hostel. The vaccine efficacy for a single dose of vaccine was - 49% (95% CI -108% to -6%), for two doses in age group 13-15 years was 63% (-43 to 90%).

Mass immunization campaign served a decisive factor for stopping of mumps epidemic in republic. The incidence of mumps cases was declined from 745,30/0000 in the period of epidemic (October 2007 – May 2008) to 16,70/0000 after the active phase of campaign (June – December 2008). The results of examination with ELISA the specific IgM antibodies in suspect mumps cases demonstrated that the number of positive reactions depends of term of serum collection and the vaccination anamnesis. The optimal term is 8-20 days after mumps onset.

The algorithm of surveillance in mumps in conditions of systematic vaccination have to include the next priority directions of activity: - surveillance and analysis mumps morbidity in function of territories, months, age groups and vaccination anamnesis; - the surveillance based on standard case definition; - the laboratory confirmation of mumps suspect cases; - the monitoring of vaccination coverage and the serological examination of the level of postvaccination immunity, determination of the age groups and the territories of high risk to mumps; - elaboration of supplementary preventive action in the cases of high risk epidemiologic situation.