Page 454 - TBE_Book_V2_2019

Chapter 14: Prevention

A subsequent long-term investigation of 18–49 years and 50–60 years age groups,
seropersistence after an Encepur booster respectively. Nevertheless, overall, a total of
vaccine was initiated, 47,48,52 and SPR were only 47 subjects (14.9%) received the second
evaluated from 2 to 10 years after the booster booster dose over the follow-up period, and
was given. After 2, 3, and 4 years, SPR of 84.9% of the study subjects were still
95.9%, 96.7%, and 93.8% were found. In seropositive after 10 years. Seropositivity rates
subjects 50–60 and>60 years of age, SPR were even higher (88.6%) in subjects below
dropped after 4 years to 93.0% and 91.7% for 50 years of age.
the 2 age groups, respectively. After 5 and 6
years, SPR in subjects below age 60 dropped to In a phase IV follow-up study published by
96% and 94%, while for subjects age 60 years Beran et al. (89) adults and adolescents who
and older, rates of 89% and 86% were had received 3 different primary vaccination
detected, respectively. Geometric mean titers schedules (rapid, conventional and accelerated
(GMTs) were also lower not only in subjects conventional) in a predecessor study and a
age 60 years and older, but also in subjects booster dose 12-18 months or 3 years after
older than 50 years. At the end of the study, 8 the primary series were followed for the
and 10 years after the booster, SPR were persistence of their TBE antibodies by yearly
86.8% and 77.3%, with a pronounced age NT determinations. Overall, ≥97% of the study
correlation, while in subjects younger than 50 subjects in the per protocol set were
years of age, seropositivity rates of 83.9% seropositive (NT titers ≥10) across all
could be detected after 10 years. In the age timepoints, regardless of the primary
group older than 50 years, only 66% of these vaccination schedule, however, older age
47
subjects remained seropositive. Similar to groups showed overall lower GMTs.
observations in young adults, seropersistence
over a 5-year period was shown for The seropersistence studies with both
adolescents who received their primary European vaccines show long-term anti-TBEV
immunization according to different immuniza- antibody persistence after the first booster
tion schedules. 16,53 vaccination, especially in the population below
50-60 years of age, whereby it should be
A prospective investigation of seropersistence mentioned that due to the different test
of TBE antibodies was recently published by systems used (different NT assays) the studies
88
Konior et al. . The study – a follow-up study of are not directly comparable.
the one in 347 adults described above,
Before results on long term seropersistence
investigated the seropersistence of TBE
antibodies up to 10 years after a primary became available a recommendation for a 10-
immunization and first booster with FSME- year booster interval starting directly after the
rd
IMMUN. The necessity for a booster 3 vaccination of the primary series was
introduced in 2006 in Switzerland. The primary
vaccination was evaluated on the basis of
goal of this change was to increase the vaccine
yearly NT determinations. As expected, the
decrease in seropositivity was more pro- coverage, which was achieved only to a
nounced in elderly as compared to younger moderate extent in some Swiss cantons in the
89
individuals - the proportion of subjects left years thereafter. Nevertheless, the increased
vaccine coverage did not cause a reduction in
potentially unprotected by prolonging the
the incidence of TBE in the country so far.
booster interval beyond 5 years was 7% in the
18–49 years age group and 18% in the 50– Therefore, very recently, the whole territory of
60 years age group. By 10 years, these Switzerland except cantons of Geneva and
proportions increased to 11% and 26% in the Ticino – is now defined as a TBE risk area,

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