Vaccine-associated measles in the low-incidence country of Korea over a 10-year period.

As the incidence of measles decreases, cases reported as suspected measles will increasingly involve rash associated with measles vaccination itself. In this study, we assessed vaccine-associated measles cases reported in Korea between 2002 and 2012 using a standardized assessment and following by the World Health Organization case definition criteria. We retrospectively analyzed data regarding (i) wild-type measles and (ii) vaccine-associated measles in patients aged 12-23 months. The presence or absence of fever, rash, cough, coryza, conjunctivitis, and Koplik spots were reviewed. Males were more likely to be reported with vaccine-associated measles than with wild-type measles (68% vs. 47%, P < 0.05). The number of patients with wild-type measles peaked between April and July, whereas that of patients with vaccine-associated measles remained relatively constant throughout the year. However, after excluding the cases reported during the 2007 outbreak in Korea, the trend was similar between the two groups. Cough, coryza, and conjunctivitis were more likely to be present in patients with wild-type measles (32-61% vs. 10-43%, P < 0.05); conversely, the absence of these symptoms was noted in most patients with vaccine-associated measles. We therefore conclude that cough, coryza, and conjunctivitis may be useful as key positive findings to distinguish between wild-type measles and vaccine-associated measles infection among 12-23-month-old patients in a country with a low incidence of measles.