7 Hepatitis A

7.4 Vaccines

7.4.1 Available vaccines

Two inactivated HAV vaccines are currently registered (approved for use) and available (marketed) in New Zealand, as well as a combined HAV and hepatitis B (HBV) vaccine and two HAV and typhoid combined vaccines.

The HAV vaccines are manufactured from cell-culture-adapted hepatitis A propagated in human fibroblasts. The HAV preparation is formalin-inactivated and adsorbed onto an aluminium adjuvant (aluminium hydroxide).

Funded vaccine

HAV vaccine is not on the Schedule, but is recommended and funded for certain high-risk groups, as shown in Table 7.1.

Havrix (GSK) contains 1440 EU (enzyme-linked immunosorbent assay [ELISA] units) of inactivated HAV adsorbed onto aluminium hydroxide. Havrix Junior contains 720 EU of inactivated HAV. Other components and residuals include aluminium hydroxide, 2 phenoxyethanol, polysorbate 20, phosphate salts, sodium chloride and formaldehyde.

Other vaccines

Inactivated HAV vaccine
Combined HAV and HBV vaccine
Combined HAV and typhoid vaccines

The two HAV-typhoid combination vaccines contain inactivated HAV and purified Salmonella typhi Vi polysaccharide.

7.4.2 Efficacy and effectivenessTop

HAV vaccines are highly immunogenic in both adults and children, with 90–100 percent of recipients developing protective antibody levels one month after the first dose.2

A second dose 6 to 18 months after the first is thought to be important for long-term protection, particularly in the absence of exposure to HAV.2, 3 In subjects with an impaired immune system, adequate anti-HAV antibody titres may not be obtained after a single dose.

HAV vaccines have not yet been approved for children aged under 12 months. The limited data on immunogenicity in infants indicates high levels of seroconversion, but those with passively acquired maternal anti-HAV have lower serum antibody titres.

HAV vaccines are highly effective in preventing clinical disease, with recorded efficacy measures of around 94–100 percent from six weeks post-vaccination. Where children, adolescents and young adults have been vaccinated in targeted and/or national programmes, there has been a rapid decline in disease incidence. This decline is through both direct and indirect (herd immunity) effects.2

Duration of immunity

Antibodies to HAV vaccine have been shown to persist in vaccinated adults for at least 15 years after vaccination, and up to 10 years in vaccinated children and adolescents. Mathematical models estimate that following completion of a two-dose series, protective levels of antibody will persist for 25 years or longer.2

7.4.3 Transport, storage and handlingTop

Transport according to the National Guidelines for Vaccine Storage and Distribution.4 Store at +2oC to +8oC. Do not freeze.

7.4.4 Dosage and administrationTop

See Table 7.2 for dosage and scheduling information.

The monovalent HAV and HAV combination vaccines should be administered by intramuscular injection into the deltoid region of the upper arm in adults and older children, or the anterolateral aspect of the thigh in infants (see section 2.3).

Co-administration with other vaccines

The US Advisory Committee on Immunization Practices (ACIP) has reported that limited data from studies in adults indicates that simultaneous administration of HAV vaccine with any one of the diphtheria, poliovirus (oral and inactivated), tetanus, typhoid (both oral and intramuscular), cholera, Japanese encephalitis, rabies or yellow fever vaccines does not decrease the immune response to either vaccine or increase the frequency of reported adverse events. Studies indicate that hepatitis B virus (HBV) vaccine can be administered simultaneously with HAV vaccine without affecting either vaccine’s immunogenicity or increasing the frequency of adverse events.5

When HAV vaccine is administered concurrently with other vaccines, it should be given in a separate syringe and needle at a different injection site.