Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1        Pharmacodynamic properties

Pharmacotherapeutic group: encephalitis vaccines, ATC Code: J07 BA01


The pharmacodynamic effect of the product consists of the induction of a sufficiently high concentration of anti-TBE antibody to provide protection against the TBE virus.

The protection rate of the previous generation TBE vaccine has been determined during a continuous surveillance as performed among the total Austrian population since 1984. In this surveillance a protection rate of above 90% after the second vaccination and above 97% after completion of the primary vaccination schedule (3 doses) was calculated.

Based on a follow up surveillance performed among the total Austrian population for the years 2000 to 2006, a protection rate of 99% was calculated with no statistically significant difference between age groups in regularly vaccinated persons. The protection rate is at least as high after the first two vaccinations, following the conventional and rapid vaccination, i.e., before completion of the basic vaccination scheme by the third vaccination. In those with a record of irregular vaccination the protection rate is significantly lower.

In clinical studies with TicoVac 0.5 ml, seropositivity was defined as an ELISA value >126 VIE U/ml or NT titers 10. Pooled seropositivity rates determined by ELISA and NT at 21 days after the second and third vaccination in the conventional and the rapid immunization schedule are presented in Table 1 and 2.

Table 1.
Conventional immunization schedule, pooled seropositivity rates 1 as determined by ELISA and NT in subjects aged 16-65 years
ELISA2                             NT2

Dose                         2nd            3rd           2nd          3rd Seropositivity rate1,%              87.5           98.7          94.8         99.4 (n/N)          (420/480)      (825/836)     (330/348)    (714/718)

Table 2.
Rapid immunization schedule, pooled seropositivity rates 1 as determined by ELISA and NT ELISA2                            NT2

Dose                          2nd            3rd          2nd          3rd Seropositivity rate of subjects aged         86.6           99.4         97.4        100.0 16-49 years, % (n/N)                (168/194)      (176/177)    (189/194)    (177/177) Seropositivity rate of subjects aged         72.3           96.3         89.0         98.8 ≥ 50 years, % (n/N)                (125/173)      (155/161)    (154/173)    (159/161) 1
– evaluated 21 days after each dose
2
- Seropositivity cut-off: ELISA >126 VIE U/ml; NT ≥ 1:10

The highest seropositivity rates as determined by ELISA and NT in both age groups were achieved upon administration of the third dose. Therefore, completion of the primary vaccination schedule of three doses is necessary to achieve protective antibody levels in almost all recipients.

Rapid immunization with TicoVac 0.5 ml resulted in high seropositivity rates determined by NT as early as 14 days after the second vaccination (89.3%) and 7 days after the third vaccination (91.7%).

Results from a follow-up study that investigated the persistence of TBE antibodies support the need for the first booster vaccination no later than three years after primary immunization. In adults aged up to 50 years seropositivity rates determined by NT remained high until 5 years after the first booster vaccination (94.3%); only slightly lower rates (>90.2%) were observed in subjects aged 50 -60 years supporting a 5-year booster interval from the first booster onwards for subjects below 60 years of age.

TicoVac vaccination induces statistically equivalent titers of TBE virus neutralizing antibodies against European, Siberian and Far Eastern TBE virus strains. In a published clinical study considerable cross- 

neutralizing antibodies were also induced against Omsk Hemorrhagic Fever Virus, however titers were lower than against the TBE virus subtypes.

A study on the persistence of immune memory in individuals from the age of 6 years and older whose vaccination intervals were longer than recommended was performed. In individuals that have received at least one primary dose in the past, a single catch-up vaccination with TicoVac 0.5 ml was able to elicit an anamnestic antibody response as measured by ELISA in 99% of adults ≥16 - <60 years and in 96% of adults ≥60 years, irrespective of the time elapsed since the last vaccination (≤ 20 years). No data are available on antibody response as measured by NT.

Pharmacokinetic Properties

5.2     Pharmacokinetic properties

Not applicable.