OBJECTIVES: FSME-Immune vaccine (FSME) is currently licensed and recommended against tick-borne encephalitis (TBE) in Austria in a three-dose primary series with an initial booster dose after three years for all ages and subsequent booster doses every three years for those ≥60 and every five years for those <60 years-of-age. Given the high effectiveness of FSME, we developed a model to assess the public health impact of a simplified schedule, changing the interval of subsequent booster doses to every 10 years after the initial booster for all ages.

METHODS: A closed-cohort Markov model was developed to track age cohorts over their lifetimes from 1-85 years. We compared the current schedule and the simplified schedule against no vaccination. In sensitivity analyses, we assumed the reduced frequency of subsequent boosters in the simplified schedule would result in increased vaccine uptake compared with the current schedule. Outcomes were the number of vaccine doses administered, adverse events (AEs), TBE cases and associated deaths. Age-specific risk and infection rates were incorporated assuming the TBEV European subtype as the primary infection agent.

RESULTS: Over 85 years, the simplified schedule would result in ~13.98 million fewer doses administered compared to the current schedule, with a corresponding reduction in AEs: 1.40 million fewer “very common” AEs, 699,098 fewer “common” AEs, 69,910 fewer “uncommon” AEs, and 6,991 fewer “rare” AEs. An estimated 55 additional TBE cases (0.64 per year) and 0.21 additional TBE-related deaths (0.002 per year) would occur overtime. In sensitivity analyses, simplified schedule prevented more TBE cases and deaths than the current schedule due to increased vaccine uptake.

CONCLUSIONS: The simplified schedule would significantly reduce number of vaccine doses administered and associated AEs without a meaningful increase in TBE cases or deaths on a per year basis. This change could simplify vaccine implementation and improve uptake while achieving better public health outcomes.