These studies demonstrate COMVAX to be highly immunogenic. The antibody responses are summarized below.

Antibody Responses to COMVAX in Infants Not Previously Vaccinated with Hib or Hepatitis B Vaccine

In the pivotal, controlled, multicenter, randomized, open-label study, 882 infants approximately 2 months of age, who had not previously received any Hib or hepatitis B vaccine, were assigned to receive a three-dose regimen of either COMVAX or PedvaxHIB plus RECOMBIVAX HB at approximately 2, 4, and 12-15 months of age. The proportions of evaluable vaccinees developing clinically important levels of anti-PRP (percent with > 1.0 mcg/mL after the second dose, n=762) and anti-HBs (percent with ≥ 10 mIU/mL after the third dose, n=750) were similar in children given COMVAX or concurrent PedvaxHIB and RECOMBIVAX HB (Table 1).

The anti-PRP response after the second dose among infants given COMVAX in this study was 72.4% (C.I. 68.7, 76.0) > 1.0 mcg/mL with a GMT=2.5 mcg/mL (C.I. 2.2, 2.8) and was comparable to that of infants given the PedvaxHIB and RECOMBIVAX HB controls which was 76.3% (C.I. 70.2, 82.5) with a GMT=2.8 mcg/mL (C.I. 2.2, 3.5). These responses exceed the response of Native American (Navajo) infants in a previous study of lyophilized PedvaxHIB (60% > 1.0 mcg/mL; GMT=1.43 mcg/mL) that was associated with a 93% reduction in the incidence of invasive Hib disease. The efficacy of COMVAX in the prevention of invasive Hib disease is expected to be similar to that obtained with monovalent lyophilized PedvaxHIB in the Protective Efficacy Trial (see CLINICAL PHARMACOLOGY, Clinical Trials with PedvaxHIB).

The anti-HBs response after the third dose among infants given COMVAX in this study was 98.4% ≥ 10 mIU/mL (C.I. 97.0, 99.3) with a GMT of 4467.5 (C.I. 3786.3, 5271.3) compared to 100.0% (C.I. 97.9, 100.0) with a GMT of 6943.9 (C.I. 5555.9, 8678.7) among infants given COMVAX or concurrent PedvaxHIB and RECOMBIVAX HB.

Although the difference in anti-HBs GMT is statistically significant (p=0.011), both values are much greater than the level of 10 mIU/mL previously established as marking a protective response to hepatitis B.^{42,44-46,51,52} These GMTs are higher than those observed in young infants who received the currently licensed regimen of RECOMBIVAX HB consisting of 5-mcg doses administered on the standard 0, 1, and 6-month schedule (GMT ~ 1359.9 mIU/mL).^53-55 In addition, two studies have shown that infants given 2.5-mcg doses of RECOMBIVAX HB according to the schedule used for COMVAX (2, 4, and 12-15 months of age) developed GMTs of 1245-3424 mIU/mL.^47,64 While a difference in GMT may result in differential retention of ≥ 10 mIU/mL of anti-HBs after a number of years, this is of no apparent clinical significance because of immunologic memory.^56,57

Because the HBsAg component of COMVAX induces a comparable anti-HBs response to that obtained with RECOMBIVAX HB, the efficacy of COMVAX is expected to be similar (Table 1).

Table 1
Antibody Responses to COMVAX, PedvaxHIB, and RECOMBIVAX HB in Infants Not Previously Vaccinated with Hib or Hepatitis B Vaccine

Antibody Responses to COMVAX in Infants Previously Vaccinated with Hepatitis B Vaccine at Birth

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