TBE Vaccination Breakthrough Cases-Does Age Matter?

Area of Science:

• Epidemiology
• Vaccinology
• Infectious Diseases

Background:

• Tick-borne encephalitis (TBE) is a significant public health concern in endemic regions.
• TBE vaccines are highly effective, with vaccine failures (VF) being rare occurrences.
• Understanding the demographics of TBE VF is crucial for optimizing vaccination strategies.

Purpose of the Study:

• To compare the age distribution of TBE cases and TBE vaccine failures (VF) across Sweden, Southern Germany, and Latvia.
• To explore potential reasons for observed differences in age distribution of TBE VF among the studied countries.
• To evaluate the scientific rationale for additional TBE vaccine priming doses in older adults (≥50 years).

Main Methods:

• Retrospective analysis of TBE case and TBE VF data from Sweden, Southern Germany, and Latvia.
• Comparison of age demographics (<50 years vs. ≥50 years) for TBE cases and TBE VF.
• Theoretical exploration of factors influencing age distribution, including diagnostic practices, vaccine uptake, behavior, and comorbidities.

Main Results:

• Age distribution of TBE cases was similar across age groups (<50 vs. ≥50 years) in all three countries.
• Sweden showed a higher proportion of TBE VF in individuals ≥50 years.
• Latvia predominantly had TBE VF in individuals <50 years, while Southern Germany exhibited a more even distribution.

Conclusions:

• Significant variations exist in the age distribution of TBE vaccine failures across different European countries.
• Factors such as diagnostic practices, vaccine uptake, and behavioral patterns may explain these demographic differences.
• There is no current scientific basis to recommend an additional priming dose of TBE vaccine for individuals aged 50 years and older.