Havrix is a vaccine indicated for active immunization against hepatitis A virus (HAV). It is approved for use in persons 12 months of age and older. Primary immunization should be administered at least 2 weeks prior to expected exposure to HAV, and protection against the virus is usually in place within one month of injection.
Havrix is administered via intramuscular route only. For children and adolescents, a single dose of 0.5 ml is administered and a 0.5 ml booster dose is required 6 to 12 months later. For adults, a single 1 ml dose is administered along with a 1 ml booster dose 6 to 12 months later.
Hepatitis A is an inflammation of the liver caused by exposure to HAV. The virus is found mostly in the stools and blood of infected persons about 15-45 days before the symptoms occur and during the first week of illness.
Symptoms of infection will usually show up 2-6 weeks after being exposed to HAV. They are usually mild, but may last for up to several months, especially in adults, and they include: dark urine, fatigue, itching, loss of appetite, low-grade fever, nausea and vomiting, pale or clay-colored stool, and yellow skin (jaundice).
No specific treatment exists for hepatitis A. Rest is recommended when symptoms are most severe, and people with acute hepatitis should avoid alcohol or any substance that is toxic to the liver, including acetaminophen. Over 85% of people with hepatitis A recover within 3 months and nearly all within 6 months; the virus does not remain in the body after the infection has gone away.
Avaxim is another hepatitis A vaccine containing inactivated HAV. It is indicated for active immunization against hepatitis A virus in susceptible adults and adolescents aged 16 years and above.
Initial protection is achieved with one single dose of the vaccine, though protection levels of antibodies may not be reached until 14 days after vaccine administration. A second (booster) dose of the vaccine should be given in order to provide long-term protection. This second dose should preferably be given between 6 and 12 months, but may sometimes be given up to 36 months after the first dose. It is predicted that HAV antibodies persist for many years (beyond 10 years) after the second dose.
The recommended dosage for subjects of at least 16 years of age is 0.5 ml for each injection.
Avaxim is intended for intramuscular administration only, and should not be administered intradermally or intravascularly. Administration in the buttocks should also be avoided, due to varying amounts of fatty tissue in this region, contributing to variability in the effectiveness of the vaccine. Under exceptional circumstances (e.g. in patients with thrombocytopenia or in patients at risk of hemorrhage), the vaccine may be injected via the subcutaneous route.
Avaxim is not recommended for use in children of 15 years of age or less, due to insufficient data on safety and efficacy.