Avaxim Mechanism of Action

Pharmacotherapeutic group: Avaxim 80 U Pediatric: Viral vaccine. Avaxim 160 U: Vaccine Against Hepatitis A. ATC code: J07BC02.
Pharmacology: Pharmacodynamics: Avaxim 80 U Pediatric: This vaccine is prepared from hepatitis A virus cultured, harvested, purified and then inactivated by formaldehyde.
It confers immunity against hepatitis A virus (HAV) by inducing anti-HAV antibody titres longer lasting and higher than those obtained after passive immunisation with immunoglobulins. This vaccine has been demonstrated to elicit protective anti-HAV antibody titres (≥20 mIU/mL) within two weeks following the injection in over 95% of individuals and in 100% of individuals before the booster dose administered 6 months after the first dose.
Two studies were conducted in Argentina (a region with intermediate endemicity for hepatitis A) to assess the long term persistence of anti-HAV antibodies.
One study (HAF83) was conducted in children (n=54) aged 12 months to 47 months vaccinated with two doses of Avaxim 80 U Pediatric six months apart. The results show antibody persistence up to 14-15 years of age at levels considered to be protective and do not suggest the need for further vaccine administrations.
A mathematical model using the available data from this study until 14-15 years after administration of the 2 doses of Avaxim 80 U Pediatric predicts a persistence of the protective anti-HAV antibodies for at least 30 years in 87.5% (CI 95%: 74.1; 94.8) of these children.
Another non-interventional study (HAF82) was conducted in children aged 11 to 23 months at the time of enrolment. All the children received routine vaccination with one dose (group 1: n=436) or two doses (group 2: n=108) of hepatitis A vaccine. After 10 years of follow-up, all the available subjects in both groups showed seroprotective levels (anti-HAV antibodies concentration ≥3 mIU/ml, using the ECLIA method). Statistical modelling based on the results of the HAF82 study including a natural booster effect predicted similar persistence of anti-HAV protective antibody titres up to 30 years, following administration of one or two doses in over 89% (CI 95%: 80; 96) to 85% (CI 95%: 70; 95) of subjects respectively.
Avaxim 160 U: This vaccine is prepared from hepatitis A virus cultured, purified and then inactivated by formaldehyde. It confers immunity against hepatitis A virus by inducing a higher antibody response than that obtained after passive immunisation with immunoglobulins. The antibodies appear soon after the first injection, and 14 days after vaccination, more than 90% of immunocompetent subjects are seroprotected (titres above 20 mIU/ml).
One month after the first injection, almost 100% of subjects have titres higher than 20 mIU/ml. Immunity may persist up to the 36^th month. In a study with 103 healthy subjects whose serology levels were monitored for 3 years after the first injection of AVAXIM 160 U, 99% still had, by the 36^th month, antibody titres of at least 20 mIU/ml against the hepatitis A virus.
Long-term persistence of a protective antibody level against the hepatitis A virus after a second dose (booster) of AVAXIM 160 U is not currently established. However, the available data suggest that the antibodies against the hepatitis A virus persist beyond 10 years after the second dose in healthy people.
Pharmacokinetics: Not applicable.
Toxicology: Preclinical safety data: Non clinical data reveal no special hazard for humans based on conventional studies of acute toxicity, repeated dose toxicity, local tolerance and hypersensitivity.