Outbreak of Measles among School Ages in Yeongju in 2000 / 한국역학회지

BACKGROUND: The outbreak of measles from 2000 to 2001 was the biggest epidemic since measles vaccination was introduced in Korea. Outbreak of measles in Yeongju was one of the earliest milestones of the nationwide outbreak in the year 2000. The authors investigated epidemiologic characteristics of the outbreak in this area. METHODS: The authors estimated attack rate through the investigation of all the school age cases of measles reported to local health authority between March and May, 2000. Case investigation was done to trace the source of the outbreak. One hundred seventy two cases were examined with medical examination, with interview on their clinical manifestations, and with serologic examination on the anti-measles IgM and IgG antibody. RESULTS: Overall attack rate among the school children was 4.3%, with highest attack rate in middle school students (8.5%). The outbreak began in March in middle schools, which spread to elementary and high schools. IgG was positive in 160(93.0%) cases and IgM was positive in 94(54.6%) cases, among which 90 cases (95.7%) were also positive for IgG. IgM positive cases had higher prevalence of rash (91.5%) compared to those without IgM (70.5%). Diagnostic criteria based on the clinical manifestation and contact history showed the highest sensitivity (92.6%) compared to conventional diagnostic criteria in outbreak (40.4-44.7%) CONCLUSIONS: High proportion of susceptible children in the population due to primary or secondary vaccine failure played a key role in this outbreak. Clinical manifestation was milder than classical measles and adjustment of diagnostic criteria can be helpful in the management of outbreak.

Seroepidemiologic Study of Measles Outbreak in a Primary School, Youngduk / 감염과화학요법

BACKGROUND: Nation-wide measles outbreaks occurred from 2000 to 2001 in Korea. Since, mass vaccination campaign for measles eradication among children and adolescents was implemented in May-August of 2001. Even in a highly vaccinated community, measles cases occur among vaccinees and there might be different serological responses among unvaccinees. In addition, the primary and secondary vaccine failures are not rare in the mass-vaccination era. Therefore, this study was undertaken to evaluate the effectiveness of serologic method for diagnosis of measles among the vaccinees and to estimate the vaccine failure rate among students with relatively high vaccination rate during the measles outbreak in a primary school. METHODS: In March 2000, the measles outbreak occurred in a primary school in Youngduk county, Kyung-sang-buk Do. Questionnaires about clinical manifestations of measles and history of measles vaccination were given out to in 209 3rd and 5th grade students among whom many measles cases occurred. The paired sera, which were taken from all students during March and May 2000, were tested for IgM and IgG measles antibody by using Enzygnost Anti-Measles IgG and IgM (Dade Behring, Germany). RESULTS: The questionnaires and serum samples were obtained from 145(69.4%) out of 209 cases. The immunization rate of measles vaccine was 80.7% (117/145). During the measles outbreak, 25 (17.2%) out of 145 cases with previous history of measles vaccination were diagnosed as measles, based on clinical definition. Among 17 cases (17/25, 68.0%) with paired samples out of 25 measles cases, 4 cases (4/17, 23.5%) were diagnosed by seroconversion of IgG, but negative IgM antibody, and they all had received measles vaccination previously. Among 117 cases with previous history of measles vaccination, 47 (40.2%) cases without measles symptoms showed four-fold increment of IgG titer. The primary and secondary failure rates of measles vaccine were 6.0% (7/117) and 1.7% (2/117), respectively. CONCLUSION: Among symptomatic measles cases with previous history of measles vaccination, 23.5% were diagnosed only by seroconversion of IgG measles antibody. In a highly vaccinated country, the accuracy of measles serodiagnosis can be increased with the IgG test of convalescent serum sample in addition to IgM antibody test. Among vaccinees, secondary immune response was 40.2%, suggesting that non-specific measles symptoms might occur among them. Therefore, further studies on the clinical definition of measles cases, vaccine failure rate and protective antibody titers should be continued in order to effectively conduct measles eradication campaign.

Seroepidemiologic Study of Measles Outbreak in a Primary School, Youngduk / 감염과화학요법

BACKGROUND: Nation-wide measles outbreaks occurred from 2000 to 2001 in Korea. Since, mass vaccination campaign for measles eradication among children and adolescents was implemented in May-August of 2001. Even in a highly vaccinated community, measles cases occur among vaccinees and there might be different serological responses among unvaccinees. In addition, the primary and secondary vaccine failures are not rare in the mass-vaccination era. Therefore, this study was undertaken to evaluate the effectiveness of serologic method for diagnosis of measles among the vaccinees and to estimate the vaccine failure rate among students with relatively high vaccination rate during the measles outbreak in a primary school. METHODS: In March 2000, the measles outbreak occurred in a primary school in Youngduk county, Kyung-sang-buk Do. Questionnaires about clinical manifestations of measles and history of measles vaccination were given out to in 209 3rd and 5th grade students among whom many measles cases occurred. The paired sera, which were taken from all students during March and May 2000, were tested for IgM and IgG measles antibody by using Enzygnost Anti-Measles IgG and IgM (Dade Behring, Germany). RESULTS: The questionnaires and serum samples were obtained from 145(69.4%) out of 209 cases. The immunization rate of measles vaccine was 80.7% (117/145). During the measles outbreak, 25 (17.2%) out of 145 cases with previous history of measles vaccination were diagnosed as measles, based on clinical definition. Among 17 cases (17/25, 68.0%) with paired samples out of 25 measles cases, 4 cases (4/17, 23.5%) were diagnosed by seroconversion of IgG, but negative IgM antibody, and they all had received measles vaccination previously. Among 117 cases with previous history of measles vaccination, 47 (40.2%) cases without measles symptoms showed four-fold increment of IgG titer. The primary and secondary failure rates of measles vaccine were 6.0% (7/117) and 1.7% (2/117), respectively. CONCLUSION: Among symptomatic measles cases with previous history of measles vaccination, 23.5% were diagnosed only by seroconversion of IgG measles antibody. In a highly vaccinated country, the accuracy of measles serodiagnosis can be increased with the IgG test of convalescent serum sample in addition to IgM antibody test. Among vaccinees, secondary immune response was 40.2%, suggesting that non-specific measles symptoms might occur among them. Therefore, further studies on the clinical definition of measles cases, vaccine failure rate and protective antibody titers should be continued in order to effectively conduct measles eradication campaign.