OBJECTIVES: In Korea, National Immunization Program(NIP) for influenza began in 1997 for elderly people aged 65 or above, and children under 6 were included in the vaccination from 2016/2017 season. However, the burden of influenza is still high. The goal of this study is to estimate the effectiveness of replacing the existing trivalent vaccine with quadrivalent vaccine to increase the matching rate. Furthermore, this study aims to measure cost effectiveness of adjuvant vaccine in the elderly.

METHODS: Cost-effectiveness analysis was conducted from societal perspective. We extracted the rates of incidence, complication, and hospitalization, and the medical costs of influenza by age groups using the National Health Insurance Service's Database from the 2013/2014 season through the 2014/2015 season. A Markov model was used for analysis in the elderly(≥65 years). However, for children(≤59 months), the decision tree model was used for analysis since aged between 6 to 64 years will be excluded from NIP. We included direct non-medical cost and caregiver's time cost. All costs and effectiveness was discounted at 3% annually.

RESULTS: From the base case analysis, compared with trivalent influenza vaccine, the quadrivalent influenza vaccine was moderately cost-effective (ICER=43,338,743 KRW/QALY) for children, and more cost-effective (ICER=20,371,157 KRW/QALY) for the elderly. Moreover, adjuvant vaccine was dominant to trivalent. Sensitivity analyses indicated that the ICER is sensitive in variance of vaccine matching rate, cost of vaccine, and distribution of influenza B.

CONCLUSIONS: Compared with trivalent influenza vaccine, the introduction of quadrivalent and adjuvant influenza vaccine would reduce influenza disease burden and be cost-effective in Korea. It is recommended to introduce quadrivalent influenza vaccine to NIP under certain conditions. Further study using a dynamic transition model seems necessary to estimate effectiveness of influenza vaccine.