The hepatitis A virus (HAV) belongs to the picornavirus family. It is one of several hepatitis viruses that cause systemic disease with pathology in the liver.

The incubation period for hepatitis A averages 28 days (range: 15 to 50 days).¹ The course of hepatitis A infection is extremely variable, ranging from asymptomatic infection to icteric hepatitis and death.²

The presence of antibodies to HAV (anti-HAV) confers protection against hepatitis A infection. However, the lowest titer needed to confer protection has not been determined.

Protective Efficacy: Protective efficacy with HAVRIX has been demonstrated in a double-blind, randomized controlled study in school children (age 1 to 16 years) in Thailand who were at high risk of HAV infection. A total of 40,119 children were randomized to be vaccinated with either HAVRIX 360 EL.U. or ENGERIX-B at 0, 1, and 12 months. 19,037 children received a primary course (doses at 0 and 1 months) of HAVRIX and 19,120 children received a primary course (doses at 0 and 1 months) of ENGERIX-B. 38,157 children entered surveillance at day 138 and were observed for an additional 8 months. Using the protocol-defined endpoint (≥2 days absence from school, ALT level >45 U/mL, and a positive result in the HAVAB-M test), 32 cases of clinical hepatitis A occurred in the control group. In the HAVRIX group, 2 cases were identified. These 2 cases were mild in terms of both biochemical and clinical indices of hepatitis A disease. Thus the calculated efficacy rate for prevention of clinical hepatitis A was 94% (95% confidence intervals 74% to 98%).³

In outbreak investigations occurring in the trial, 26 clinical cases of hepatitis A (of a total of 34 occurring in the trial) occurred. No cases occurred in vaccinees who received HAVRIX.

Using additional virological and serological analyses post hoc, the efficacy of HAVRIX was confirmed. Up to 3 additional cases of very mild clinical illness may have occurred in vaccinees. Using available testing, these illnesses could neither be proven nor disproven to have been caused by HAV. By including these as cases, the calculated efficacy rate for prevention of clinical hepatitis A would be 84% (95% confidence intervals 60% to 94%).

In a study designed to interrupt an epidemic of hepatitis A among Native Americans in Alaska, vaccination with a single dose of HAVRIX (1440 EL.U./mL in adults, 720 EL.U./0.5 mL in children and adolescents) appeared to be efficacious.⁴

Immunogenicity in Children and Adolescents: Immune Response to HAVRIX 720 EL.U./0.5 mL in Children Vaccinated Beginning at 11 Months of Age: In a prospective, open-label, multicenter study, 1,085 children were enrolled into one of 5 groups:

(1) children 11 to 13 months of age who received HAVRIX on a 0- and 6-month schedule;

(2) children 15 to 18 months of age who received HAVRIX on a 0- and 6-month schedule;

(3) children 15 to 18 months of age who received HAVRIX coadministered with INFANRIX® (Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Adsorbed) and OMNIHIB Haemophilus b Conjugate Vaccine (Tetanus Toxoid Conjugate) [Hib conjugate vaccine (PRP-T)] at month 0 and HAVRIX at month 6;

Brand Name: Havrix
Generic Name: Hepatitis A Vaccine, Inactivated

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