ABSTRACT
OBJECTIVES: This study was performed to investigate the mumps transmission control status and inapparent infection rate among middle and high school students in Daegu City during a mumps outbreak. METHODS: Nine schools (two middle schools and seven high schools), which reported a number of mumps cases between 2007 and 2008 were selected for investigation. During March-May 2008, a standard questionnaire was distributed to gather information about case identification, instructed isolation measure, isolation status of mumps cases and related factors, and outdoor activities of non-isolated mumps case. Inapparent infection rate was estimated by serum mumps IgM and IgG antibodies status and self-reported mumps symptoms in three of the nine schools. RESULTS: Among 2,560 respondents, more than half of students answered that they did not receive instructions in mumps transmission control measures during the outbreak. Among the 327 mumps cases identified by the questionnaire, 131 cases (40.1%) were considered as isolated and the isolation rates were significantly different among schools, grades, and gender. Of the non-isolated cases, 88.3% continued attending school. Inapparent mumps infection rates were between 56.3% and 70.2%. CONCLUSIONS: Mumps transmission control was inadequate to control the mumps outbreak. Although high inapparent infection rate would mitigate the transmission control effect of case isolation, this measure is fundamental for infection control. The reasons of this inadequate status need to be explored to develop an effective intervention strategy.
Subject(s)
Adolescent , Child , Female , Humans , Male , Communicable Disease Control/methods , Disease Outbreaks/statistics & numerical data , Immunoglobulin G/blood , Immunoglobulin M/blood , Mumps/epidemiology , Patient Isolation , Surveys and Questionnaires , Republic of Korea/epidemiology , Schools/statistics & numerical data , StudentsABSTRACT
PURPOSE: Despite of the high MMR vaccine coverage, the mumps outbreaks is continued in most developed countries including South Korea. To evaluate the effectiveness of MMR vaccine, we carried out mumps outbreak investigation in one kindergarten. METHODS: In Dec. 2006, a mumps outbreak occurred in a kindergarten. Retrospective study was conducted among 212 respondents (205 children and 7 teachers) in 230 study populations (study participation rate: 92%). To define mumps cases, a questionnaire survey, telephone survey, and mumps antibody test with serum were conducted. MMR vaccination status was verified in 198 children using children's vaccination records, National Immunization Registration System and/or medical records of private clinics or hospitals. RESULTS: Over 90% children had received one dose of MMR vaccination. However, 2nd dose of MMR vaccination rate was 45.1%. Attack rates of mumps were 22.9%(22/96) for one dose MMR vaccinees and 3.3%(3/92) for two doses vaccinees. MMR vaccine effectiveness of two doses over one dose was 86%. Mumps attack rate in one dose MMR vaccinees increased by the duration after MMR vaccination. Among all mumps cases, asymptomatic mumps infection identified by IgM positive or IgG over 10,000mIU/ml was 58% (26/ 45). CONCLUSIONS: MMR one dose coverage rate was high(92.1%), but the second dose vaccination rate was very low (45.1%). Mumps attack rate was increased by the duration after the MMR vaccination, and the maximum effectiveness of one dose MMR vaccination was low (77.1%). Therefore, to prevent mumps outbreaks in the kindergarten, second MMR vaccination should be scheduled in 4 years old age, and the coverage rate should be increased over 90%. Further studies for the effectiveness of MMR two doses after 5 and more years are needed.