Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1    Pharmacodynamic properties

Pharmacotherapeutic group: Hepatitis A vaccines, ATC code J07BC02

Mechanism of action
Havrix confers immunisation against HAV by stimulating specific immune responses evidenced by the induction of antibodies against HAV.

Pharmacodynamic effects

The immunogenicity of Havrix was assessed in 39 studies in more than 6 000 subjects including adults, adolescents and children.

Immune response

In clinical studies, 99% of vaccinees seroconverted 30 days after the primary dose.
In a subset of adult clinical studies where the kinetics of the immune response were studied, early and rapid seroconversion was demonstrated following administration of the primary dose of Havrix 1440 Adult in 79% of vaccinees at day 13, 86.3% at day 15, 95.2% at day 17 and 100% at day 19.

In clinical studies involving children 1-18 years of age, specific humoral antibodies against HAV were detected in more than 93% of vaccinees at day 15 and 99 % of vaccinees one month following administration of the primary dose of Havrix 720 Junior.

Immune response in patients with chronic liver disease

In two clinical trials, 300 subjects with chronic liver disease (chronic hepatitis B, chronic hepatitis C or other) were vaccinated with 2 doses of Havrix 1440 Adult given at an interval of 6 months. The vaccine provided detectable antibody titres in at least 95% of the vaccinees, one month after the second dose.

Persistence of the immune response

In order to ensure long-term protection, a booster dose should be given between 6 and 12 months after the primary dose of Havrix 720 Junior or Havrix 1440 Adult. In clinical trials, all vaccinees were seropositive one month after the booster dose.

Long-term persistence of hepatitis A antibody titres following 2 doses of Havrix 1440 Adult given 6 to 12 months apart has been evaluated. In two clinical trials in adults, 96.7% and 100% of vaccinees were still seropositive at year 17.5 (study HAV-112) and year 17 (study HAV-123), respectively.
Data available up to 17 and 17.5 years allow prediction that at least 95% and 90% of subjects will remain seropositive (≥15 mIU/ml) 30 and 40 years after vaccination, respectively.
Current data do not support the need for further booster vaccination among immunocompetent subjects after a 2-dose vaccination course.

It can be expected that the duration of protection in children following 2 doses of Havrix 720 Junior is comparable with the above predicted duration of protection in adults.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties

Evaluation of pharmacokinetic properties is not required for vaccines.