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 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.
A study conducted in Argentina (an area of intermediate endemicity for hepatitis A) enabled the evaluation of long term persistence of anti-HAV antibodies in children aged 12 months to 47 months vaccinated with 2 doses of Avaxim 80 U Pediatric 6 months apart. The results show a persistence of the antibodies until 14-15 years at levels considered as protective and do not suggest the need for new administration of the vaccine.
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.
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.