Page 457 - TBE_Book_V2_2019

Chapter 14: Prevention

after a documented history of 2 vaccinations, Prevention, of the Hailar Railway, which
thus achieving a vaccine effectiveness of 100% showed that since the use of the current
after 2 vaccinations. A later investigation of generation TBE vaccine, no TBE cases had
6
vaccine effectiveness for the years 2000- been reported in 2009 and 2010. However,
36
2011 showed a slight decrease of vaccination details of the vaccination program (vaccina-
coverage to 85% in 2011. Nevertheless, similar tion schedule, type of surveillance, etc.) are
high rates of effectiveness were seen: 98.7% largely unknown.
and 96.3% for regularly vaccinated subjects
under best- and worst-case assumptions, Vaccination failures
respectively, and 92.5% and 91.3% for
irregularly vaccinated subjects under best- and Vaccine failures have been reported only
worst-case scenarios, respectively. These occasionally. A retrospective investigation of
findings highlight the importance of adhering breakthrough cases over a period of 8 years
65
to the recommended vaccination schedule, as was conducted in Sweden. During this
there is a considerably higher risk of acquiring period, 19 verified and 8 probable cases of
TBE in irregularly vaccinated subjects. As a TBE vaccine failures were reported. No
result of the high vaccination uptake in accepted and plausible rationale exists to
Austria, an estimated 4,000 TBE cases and 20 explain the immunological mechanisms
deaths were prevented between 2000 and leading to a vaccination failure. Therefore, it is
2011. 35,36 During the same time, neighboring not clear whether primary low-level
countries including the Czech Republic and responsiveness after regular TBE vaccination
Slovenia, which are also highly endemic for may be a risk factor for vaccine breakthrough.
TBE but with very low vaccination coverage In contrast to unvaccinated subjects, most
(16% in 2009 and 12% in 2008, respective- patients with breakthrough disease already
ly), 36,64 experienced an increase in disease had high antibody avidity and strong
incidence. neutralizing antibodies in the first sample
taken after hospitalization. When combined
In the context of a mass immunization with an observed delayed immunoglobulin M
program that started in 1996 in the highly (IgM) antibody response, and therefore
endemic region of Sverdlovsk in Russia, an presenting the features of an anamnestic
impressive decrease in TBE incidence could be response, this immune profile was obviously
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achieved – from 42.1/100,000 in 1996 to not sufficient to prevent the disease.
9.7/100,000 in 2000 to 5.1/100,000 in 2006.
The vaccines used were TBE- Moscow (market
share 80%); EnceVir (market share 6%); FSME-
IMMUN (market share 12%); and Encepur Safety and tolerability
(market share 2%). Based on these data, an
The currently available European TBE vaccines
overall vaccine effectiveness of 62% and 89% 8,33
have a well-established safety record.
was estimated for the years 2000 and 2006,
31
respectively. Nevertheless, rare cases of Safety and tolerability have been investigated
TBE breakthrough disease, primarily in in a number of clinical studies conducted in
children and adults. Broad experience also
subjects older than 50 years of age, have been
comes from the field, with extensive
reported after primary TBE vaccination but not
after booster immunization. 65-68 pharmacovigilance over many years. Over the
No effectiveness data are available for the past decades, TBE vaccine formulations have
Chinese vaccine. There is only a single report, been refined, thereby significantly reducing
reactogenicity. In contrast, little published
from the Center for Disease Control and
data are available on the safety of the 2

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