Evaluation of an Expanded Case Definition for Vaccine-Modified Measles in a School Outbreak in South Korea in 2010

Abstract

SUMMARY:In this study, we have described the clinical characteristics of vaccine-modified measles to assess the performance of an expanded case definition in a school outbreak that occurred in 2010. The sensitivity, specificity, and the positive and negative predictive values were evaluated. Among 74 cases of vaccine-modified measles, 47 (64z) met the original case definition. Fever and rash were observed in 73z (54/74); fever was the most common (96z, 71/74) presenting symptom, and rash was noted in 77z (57/74) of the cases. The original case definition showed an overall sensitivity of 63.5z and a specificity of 100.0z. The expanded case definition combining fever and rash showed a higher sensitivity (72.9z) but a lower specificity (88.2z) than the original. The presence of fever and one or more of cough, coryza, or conjunctivitis scored the highest sensitivity among the combinations of signs and symptoms (77.0z), but scored the lowest specificity (52.9z). The expanded case definition was sensitive in identifying suspected cases of vaccine-modified measles. We suggest using this expanded definition for outbreak investigation in a closed community, and consider further discussions on expanding the case definition of measles for routine surveillance in South Korea.

Resurgence of measles in a country of elimination: interim assessment and current control measures in the Republic of Korea in early 2014

“…[4][5][6] Given the very low measles incidence in the ROK, newly trained healthcare professionals are less aware of and have less experience with measles; furthermore, the vaccine-modified clinical presentation hampers clinical diagnosis. 7 Also, identifying the chain of transmission is challenging in dense urban areas. Misdiagnosed measles cases come into prolonged, close contact with school or work colleagues, without adequate precautions or isolation, potentially resulting in secondary vaccine failure related with waning immunity.…”

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“…Delayed recognition was caused by the atypical measles symptoms of mild fever and rash among students. In 2010, students infected with measles at a middle school in the city of Incheon showed an atypical clinical course of measles [ 8 ]. Those students may have had a less than optimal measles immunity status, and they were continuously exposed to measles at school.…”

Measles Elimination Activities in the Western Pacific Region: Experience from the Republic of Korea

“…The two unexpected outbreaks of measles that occurred during 2006 in a kindergarten in Incheon, and during 2007 in which cases that were mostly nosocomial transmission ( 37 38 ). In 2010, an outbreak occurred in a junior high school that included 74 vaccine-modified measles cases with limited symptoms that resembled measles ( 39 ).…”