Immunogenicity in Adults: In 3 clinical studies involving over 400 healthy adults 18-50 years of age given a single 1440 EL.U. dose of HAVRIX, specific humoral antibodies against HAV were elicited in more than 96% of subjects when measured 1 month after vaccination. By day 15, 80% to 98% of vaccinees had already seroconverted (anti-HAV ≥20 mIU/mL [the lower limit of antibody measurement by current assay]). Geometric mean titers (GMTs) of seroconverters ranged from 264 to 339 mIU/mL at day 15 and increased to a range of 335 to 637 mIU/mL by 1 month following vaccination.⁵

The GMTs obtained following a single dose of HAVRIX are at least several times higher than that expected following receipt of immune globulin (IG).

In a clinical study using 2.5 to 5 times the standard dose of IG (standard dose = 0.02 to 0.06 mL/kg), the GMT in recipients was 146 mIU/mL at 5 days post-administration, 77 mIU/mL at month 1, and 63 mIU/mL at month 2.5

In 2 clinical trials in which a booster dose of 1440 EL.U. was given 6 months following the initial dose, 100% of vaccinees (n = 269) were seropositive 1 month after the booster dose, with GMTs ranging from 3,318 mIU/mL to 5,925 mIU/mL. The titers obtained from this additional dose approximate those observed several years after natural infection.

In a subset of vaccinees (n = 89), a single dose of HAVRIX 1440 EL.U. elicited specific anti-HAV neutralizing antibodies in more than 94% of vaccinees when measured 1 month after vaccination. These neutralizing antibodies persisted until month 6. One hundred percent of vaccinees had neutralizing antibodies when measured 1 month after a booster dose given at month 6.

Immunogenicity of HAVRIX was studied in subjects with chronic liver disease of various etiologies. 189 healthy adults and 220 adults with either chronic hepatitis B (n = 46), chronic hepatitis C (n = 104), or moderate chronic liver disease of other etiology (n = 70) were vaccinated with HAVRIX 1440 EL.U. on a 0- and 6-month schedule. The last group consisted of alcoholic cirrhosis (n = 17), autoimmune hepatitis (n = 10), chronic hepatitis/cryptogenic cirrhosis (n = 9), hemochromatosis (n = 2), primary biliary cirrhosis (n = 15), primary sclerosing cholangitis (n = 4), and unspecified (n = 13). At each time point, GMTs were lower for subjects with chronic liver disease than for healthy subjects. At month 7, the GMTs ranged from 478 mIU/mL (chronic hepatitis C) to 1,245 mIU/mL (healthy), as determined by a commercial ELISA. The relevance of these data to the duration of protection afforded by HAVRIX is unknown. One month after the first dose, seroconversion rates in adults with chronic liver disease were lower than in healthy adults. However, 1 month after the booster dose at month 6, seroconversion rates were similar in all groups; rates ranged from 94.7% to 98.1%.

The duration of immunity following a complete schedule of immunization with HAVRIX has not been established.

Immune Response to Concomitantly Administered Vaccines: The concomitant administration of Hib conjugate vaccine (PRP-T) and INFANRIX with HAVRIX was evaluated in children receiving their first dose of HAVRIX at 15 to 18 months of age followed by a second dose of HAVRIX 6 months later. One month after the second dose of HAVRIX, the anti-hepatitis A vaccine response (100%) in those receiving the first dose of HAVRIX coadministered with INFANRIX and Hib conjugate vaccine (PRP-T) was shown to be non-inferior to that achieved (100%) in 15 to 18 month olds who received HAVRIX alone (lower limit of 95% CI on difference for coadministered vaccine group minus HAVRIX alone group >-5%).

One month after vaccination with Hib conjugate vaccine (PRP-T), the seroprotection rates for Hib were shown to be non-inferior in subjects who received Hib conjugate vaccine (PRP-T) concomitantly with their first dose of HAVRIX (100% achieved ≥1 mcg/mL of anti-PRP antibody; 95% CI, 97 to 100%) as compared to those who did not receive HAVRIX (100% achieved ≥1 mcg/mL of anti-PRP antibody; 95% CI, 97 to 100%). Both groups received INFANRIX concomitantly with Hib conjugate vaccine (PRP-T) ± HAVRIX. Insufficient data are available to assess the immune response of a fourth dose of DTaP vaccine when administered with HAVRIX.

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