Epidemiology of Varicella in Korea Based on Pediatrician's Office Practice

ABSTRACT

PURPOSE: Although varicella outbreakes have frequently occured, the epidemiology of varicella in Korea has not well been delineated. Furthermore without enough investigation with regard to safety and efficacy of varicella vaccine in Korean population, the vaccine has begun to be used in healthy children. Therefore the authors analized the clinical features of patients diagnosed of varicella to aid in understanding the epidemiology of varicella in Korea, and also compared the difference depending on varicella vaccination status. METHODS: The study population consisted of 1154 otherwise healthy patients diagnosed of varicella by six private pediatricians (5 in Seoul and 1 in Incheon) from March 1994 to February 1996. The information pertaining to clinical features of varicella was obtained through questionnaires answered by pediatricians. RESULTS: 1) Among the total 1154 patients, sex ratio was 1.2:1 with male predominance. The average age was 4.1+/-2.5 years old with the range of 1 month to 15 years of age. One thousand and thirty patients (89.2%) were younger than 6 years old and 126 patients (10.9%) were younger than 1 year old. 2) Occurrence of varicella was reported every month during the study period and peak in June, July, and November to January. 3) Two hundreds and eight-four patients (24.6%) had a history of previous varicella vaccination. 4) Four hundreds and fifty-five patients (53.3%) had a history of exposure to patients with varicella and the mean incubation period was 13.7+/-4.1 days with no difference according to varicella vaccination status. 5) Prodromal symptoms were reported from 615 patients (53.3%) with temperature elevation being most frequent. Except for temperature elevation, occurrence of all other prodromal symptoms was not different between unvaccinated and vaccinated patients. 6) Duration of new rash development was 3.9+/-1.3 days with the range of 1 to 9 days and longer in unvaccinated patients (4.1+/-1.2 days) compared to vaccinated patients (3.1+/-1.1 days). Atypical rash was observed in 144 patients (12.5%) and more frequently among unvaccinated patients. 7) Sixty-eight patients suffered from complications which were skin infection (49), conjunctivitis (20), neurologic complication (1), and pneumonia (1), with no difference between unvaccinated and vaccinated patients. CONCLUSIONS: The current study is reporting, for the first time, the epidemiologic features of varicella in Korea. Bedsides, the result of the study, illustrating that 1/4 of the patients reported to have varicella were vaccinated with varicella vaccine, indicates the necessity of the investigation for the safety and efficacy of the vaccine in Korean population.