Trend of measles morbidity in Thailand

Measles is still an important public health problem in Thailand despite the high coverage of measles vaccination since 1984, and the second dose of measles vaccination in primary school children in 1991.

To study the trend of measles morbidity in Thai children.

Review of the Annual Epidemiological Surveillance Report of the Epidemiology Section, Department of Communicable Disease Control, Ministry of Public Health (MOPH), and hospital records of measle cases at the Queen Sirikit National Institute of Child Health (QSNICH) (Bangkok Children's Hospital). Paired t-test and analysis of variance (ANOVA) were used for data analysis in the present study.

Before 1984, measles morbidity was very high, at the level of 52.3 to 93.67 per 100,000 population. After measles vaccine was included in the EPI (Expanded Program on Immunization), the morbidity fluctuated for some years, and the group of children infected with measles changed from under 5 years to the age group of 5-9 years old. So a second dose of measles vaccine was added to the EPI given to children in Prathom 1 (first year in primary school, 6 years old and over). After 4 years of adding the second dose of measles in the EPI, measles cases was still present in a significant number in both the under 5 and 5-9 age groups. From the statistics of measles cases at the QSNICH, with an average of 736 measles cases per year, the number of measles cases is now decreasing, but the incidence of measles is still high in both the under 5 and 5-9 age groups.

According to the EPI in Thailand, children were given measles vaccine at the age of 9 months which is when seroconversion was significantly lower than immunization after one year of age. The trend of measles morbidity is decreasing, but is still high in children in the under 5 and 5-9 age groups. Vaccine failure may be one of the contributing factors of measles cases in children in these age groups. A booster dose of measles vaccine at 15-18 months old is suggested in order to increase the seroprotection in children in the under 5 and 5-9 age groups.