Beran et al.
Sustained antibody persistence for at least 15 years after a booster vaccination against tick-borne encephalitis following different primary vaccination schedules: Third 5-year follow-up.
Vaccine. 2023;41(23):3518-3524. doi:10.1016/j.vaccine.2023.04.061

After a complete primary immunization and a first booster injection with TBE vaccine, the recommended interval in most countries for a booster vaccination is five- or three-years depending on the age of the vaccinee.

However, the duration of protection (by neutralizing antibodies) after the first booster vaccination is not yet known, and the optimal booster interval is debated (see e.g., Newsletter June 2022, February 2022, Newsletter November 2021).

In a phase-IV, open-label extension study in a single center in the Czech Republic carried out between October 2017 and October 2021, neutralizing TBE antibodies titers (NT) were measured in sera from individuals, who had received a primary vaccination and one booster vaccination with Encepur (based on TBE virus strain K23) by different vaccination schedules (adolescents or adults at time of first injection).

The vaccinations schedules were as follows:

  • rapid: day 0, 7, 21
  • conventional: day 0, 28, 300
  • accelerated: day 0, 14, 300
  • modified conventional (not licensed): day 0, 21, 300

A neutralizing titer of 10 (based on the homologous strain K23) was considered as clinically meaningful threshold and surrogate for protection.

15 years after the first booster, ≥98.5% of the participants had a TBE NT of ≥10, regardless of the primary vaccination schedule they had received.

NT geometric mean titers were similar in all study groups far above the threshold of NT 10 and remained high among participants ≥50 years old (NT range 98–206) and ≥60 years old (NT range 91–191) across study groups and time points.

These results indicate that the possibility of prolonging the interval for subsequent booster vaccinations after the first booster should be considered.

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