A serious complication of acute hepatitis B virus infection is massive hepatic necrosis while sequelae of chronic hepatitis B include cirrhosis of the liver, chronic active hepatitis, and hepatocellular carcinoma. Chronic carriers of HBsAg appear to be at increased risk of developing hepatocellular carcinoma. Although a number of etiologic factors are associated with development of hepatocellular carcinoma, the single most important etiologic factor appears to be chronic infection with hepatitis B virus.³⁶ According to the CDC, hepatitis B vaccine is recognized as the first anti-cancer vaccine because it can prevent primary liver cancer.⁶⁷

The vehicles for transmission of the virus are most often blood and blood products but the viral antigen has also been found in tears, saliva, breast milk, urine, semen, and vaginal secretions. Hepatitis B virus is capable of surviving for days on environmental surfaces exposed to body fluids containing hepatitis B virus. Infection may occur when hepatitis B virus, transmitted by infected body fluids, is implanted via mucous surfaces or percutaneously introduced through accidental or deliberate breaks in the skin. Transmission of hepatitis B virus infection is often associated with close interpersonal contact with an infected individual and with crowded living conditions.³⁷

Prevention of Hepatitis B Disease with Vaccine

Hepatitis B infection and disease can be prevented through immunization with vaccines that contain viral surface antigen (HBsAg) and induce formation of protective antibody (anti-HBs).^38-39

Multiple clinical studies have defined a protective level of anti-HBs as 1) 10 or more sample ratio units (SRU or S/N) as determined by radioimmunoassay or 2) a positive result as determined by enzyme immunoassay.^40-46 Note: 10 SRU is comparable to 10 mIU/mL of antibody.³⁶ The ACIP and an international group of hepatitis B experts consider an anti-HBs titer ≥ 10 mIU/mL an adequate response to a complete course of hepatitis B vaccine and protective against clinically significant infection (antigenemia with or without clinical disease).^36,46

Clinical Trials with RECOMBIVAX HB

In clinical studies, 100% of 92 infants under 1 year of age born of non-carrier mothers developed a protective level of antibody (anti-HBs ≥ 10 mIU/mL) after receiving three 5-mcg doses of RECOMBIVAX HB at intervals of 0, 1, and 6 months.³¹

In one clinical study of RECOMBIVAX HB (2.5 mcg), which examined a different regimen of RECOMBIVAX HB, protective levels of antibody were achieved in 98% of 52 healthy infants vaccinated at 2, 4, and 12 months of age. Protective anti-HBs levels were achieved in 100% of 50 infants vaccinated at 2, 4, and 15 months of age.⁴⁷

The protective efficacy of three 5-mcg doses of RECOMBIVAX HB, given at birth (with Hepatitis B Immune Globulin), 1, and 6 months of age, has been demonstrated in neonates born of mothers positive for both HBsAg and HBeAg (a core-associated antigenic complex which correlates with high infectivity). In this trial, after nine months of follow-up, chronic infection had not occurred in 96% of 130 infants.⁴⁸ The estimated efficacy in prevention of chronic hepatitis B infection was 95% as compared to the infection rate in untreated historical controls.⁴⁹

Immunogenicity of COMVAX

The immunogenicity of COMVAX (7.5 mcg Haemophilus b PRP, 5 mcg HBsAg) was assessed in 1602 infants and children 6 weeks to 15 months of age in 5 clinical studies. In 2 controlled clinical trials (n=684), the immune response of COMVAX was compared with that obtained using the monovalent vaccines, PedvaxHIB (7.5 mcg Haemophilus b PRP) and RECOMBIVAX HB (5 mcg HBsAg) given at separate sites, either concurrently or one month apart. The immunogenicity of COMVAX was further assessed in 2 uncontrolled studies (n=852). In the first, a complete three-dose series of COMVAX was administered concurrently with other routine pediatric vaccines. In the second, COMVAX was administered as the third dose of Haemophilus b PRP and HBsAg concurrently with routine pediatric vaccines. COMVAX was also administered as the control arm in the evaluation of an investigational vaccine (n=66).

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