The changing epidemiology of hospitalized pediatric patients in three measles outbreaks.

OBJECTIVES

To assess the demographic and clinical findings of measles patients during three epidemics from 1989 to 2001.

METHODS

A total 520 medical records of measles patients were analyzed retrospectively and divided into three groups; those who were admitted during 1989-1990 (group I, 116 patients), those admitted during 1993-1994 (group II, 127 patients), and those admitted during 2000-2001 (group III, 277 patients).

RESULTS

For the age distribution, there was no difference in the proportion of < 2 years of age (61%, 58% and 57%, respectively) for the three groups. However, in each outbreak, there were significant differences in the distribution of > or = 2 years children who had mostly received one-dose measles-mumps-rubella (MMR) vaccination. The age distribution had changed with a significant increase in older children in subsequent outbreaks. In the last 2000-2001 outbreak, there was a pattern for increased attack rates with increasing interval since the initial vaccination. There was no statistical difference between the three groups in gender ratio, MMR vaccination rate in > or = 2 years of age, duration of fever, and complications. No difference was found in all the clinical and laboratory parameters between the anti-measles IgM antibody negative patients and the positive patients.

CONCLUSIONS

The age distribution of admitted children with measles in each outbreak has changed over time since the introduction of one-dose MMR vaccination. This finding suggests that the secondary vaccine failure may have played a large role in the last measles outbreak.