Epidemiology and burden of Haemophilus influenzae disease in Thai children before implementation of the routine immunisation programme: A National Health Data Analysis

Objectives: To conduct the first pre-Haemophilus influenzae (Hi) type b (Hib) immunisation programme-based epidemiological study using national health data. Methods: We analysed National Health Security Office data, which cover 72% of the Thai population. The study population included children aged <18 years admitted for Hi disease from 2015 to 2019. Hi disease diagnosis and death were based on the International Statistical Classification of Diseases and Related Health Problems (10th revision) hospital discharge summary codes. We estimated the hospital cost per admission using diagnosis-related grouping with a global budget. Results: A total of 1125 children aged <18 years were admitted for Hi disease. During the 5-year-study, the annual incidence of Hi disease varied from 1.5 to 1.9 per 100,000 children, with an overall case fatality rate (CFR) of 2%. Pneumonia was the most common clinical form, followed by meningitis and sepsis. The incidence, clinical forms and severity of Hi disease were age specific. Infant CFR was higher than that of other age groups. The incidence of Hi disease in children aged <5 years was 4.9 per 100,000 (CFR = 2.0%). Sepsis was the primary cause of infant death, whereas pneumonia was the cause of death in children aged >5 years. The hospital cost ranged from 25,000 to 30,000 THB per admission. Conclusions: This analysis provided epidemiological data of Hi in Thai children before the Hib routine immunisation programme. The incidence of Hi disease was lower than that previously speculated. Our results could facilitate an assessment of the impact of Hib immunisation programme in Thailand.