Background: The current coronavirus disease 2019 (COVID-19) outbreak has caused a persistent decline in childhood vaccination coverage, including Haemophilus influenzae type b (Hib) vaccine, in some countries. Our objective was to evaluate the impact of decreased Hib vaccination due to COVID-19 on invasive Hib disease burden in Japan. Methods: Using a deterministic dynamic transmission model (susceptible-carriage-infection-recovery model), the incidence rates of invasive Hib disease in under 5 year olds in rapid vaccination recovery and persistent vaccination declined scenarios were compared for the next 10 years after 2020. The national Hib vaccination rate after the impact of COVID-19 reduced to 87% and 73% in 2020 from approximately 97% each in 2013-2019 for primary and booster doses. Results: While the persistent decline scenarios revealed an increase in invasive Hib disease incidence to 0.50/100,000 children under 5 years old, the incidence of the rapid recovery scenario slightly increased with a c