(Q) Trends in The Incidence of Varicella Cases with Complications Among Korean Children During 2010-2020 After the Universal One-Dose Varicella Vaccination Program

Publication Number: 1016

Background: Varicella (chickenpox) infection, albeit mostly mild or moderate, can cause serious neurological and infectious complications, leading to hospitalization, permanent sequelae, or death in some cases. Only a few studies have examined the impact of one-dose vaccination against varicella zoster virus on the incidence of varicella cases with complications among children using standard disease classification codes at a national level.

Objectives: To determine whether the incidence of varicella cases with complications had decreased during 2010-2020 among Korean children after the introduction of the universal one-dose varicella vaccination program in 2005.

Methods: For this study, open access nationwide healthcare claim data from the Korea Health Insurance Review and Assessment Service (HIRA), publicly available through the healthcare big data open system (https://opendata.hira.or.kr), were used. In the data, varicella cases with complication were recorded according to the International Classification of Disease, 10th revision (ICD-10). Annual incidence rates of varicella cases with complications were estimated by dividing the numbers of age-specific (0-4, 5-9, 10-14, and 15-19 years) varicella cases with complications in the HIRA data by the age-specific total population sizes in each year from 2010 to 2020. In addition, complication-specific analysis was performed: meningitis (B010), encephalitis, myelitis and encephalomyelitis (B011), pneumonia (B012), and other complications (B018).

Results: The incidence of varicella cases with complications among Korean children has significantly (92%) decreased from 137 per 100,000 persons in 2010 to 11 per 100,000 persons in 2020. The incidence drop was greatest during 2010-2013 and afterward attenuated to some extent, although it continued until 2020 (e.g., the incidence was 24 per 100,000 persons in 2019 before the pandemic of the coronavirus disease-19). In the sub-analyses, the decrease in the incidence of varicella cases with complications was greater for children aged 0-4 (96%) and aged 5-9 (92%) than children aged 10-19 (77-78%). It was greatest for varicella ‘pneumonia’ (98%), followed by ‘other complications’ (92%), ‘meningitis’ (73%), and ‘encephalitis, myelitis and encephalomyelitis’ (71%).

Conclusions: This study implies that the universal one-dose varicella vaccination program introduced in 2005 has been successful for the prevention of severe incident varicella cases among Korean children.