ENGERIX-B — hepatitis b virus subtype adw2 hbsag surface protein antigen injection, suspension
Dispensing Solutions Inc.
ENGERIX-B [Hepatitis B Vaccine (Recombinant)] is a noninfectious recombinant DNA hepatitis B vaccine developed and manufactured by GlaxoSmithKline Biologicals. It contains purified surface antigen of the virus obtained by culturing genetically engineered Saccharomyces cerevisiae cells, which carry the surface antigen gene of the hepatitis B virus. The surface antigen expressed in Saccharomyces cerevisiae cells is purified by several physicochemical steps and formulated as a suspension of the antigen adsorbed on aluminum hydroxide. The procedures used to manufacture ENGERIX-B result in a product that contains no more than 5% yeast protein. No substances of human origin are used in its manufacture.
ENGERIX-B is supplied as a sterile suspension for intramuscular administration. The vaccine is ready for use without reconstitution; it must be shaken before administration since a fine white deposit with a clear colorless supernatant may form on storage.
ENGERIX-B is formulated without preservatives.
Each 0.5-mL dose contains 10 mcg of hepatitis B surface antigen adsorbed on 0.25 mg aluminum as aluminum hydroxide. The pediatric formulation contains sodium chloride (9 mg/mL) and phosphate buffers (disodium phosphate dihydrate, 0.98 mg/mL; sodium dihydrogen phosphate dihydrate, 0.71 mg/mL).
Each 1-mL adult dose contains 20 mcg of hepatitis B surface antigen adsorbed on 0.5 mg aluminum as aluminum hydroxide. The adult formulation contains sodium chloride (9 mg/mL) and phosphate buffers (disodium phosphate dihydrate, 0.98 mg/mL; sodium dihydrogen phosphate dihydrate, 0.71 mg/mL).
Several hepatitis viruses are known to cause a systemic infection resulting in major pathologic changes in the liver (e.g., A, B, C, D, E, and G). The estimated lifetime risk of HBV infection in the United States varies from almost 100% for the highest-risk groups to less than 20% for the population as a whole.1 Hepatitis B infection can have serious consequences including acute massive hepatic necrosis, chronic active hepatitis, and cirrhosis of the liver. Up to 90% of neonates and 6% to 10% of adults who are infected in the United States will become hepatitis B virus carriers.1 It has been estimated that 200 to 300 million people in the world today are persistently infected with hepatitis B virus.1 The Centers for Disease Control and Prevention (CDC) estimates that there are approximately 1 to 1.25 million chronic carriers of hepatitis B virus in the United States.1 Those patients who become chronic carriers can infect others and are at increased risk of developing primary hepatocellular carcinoma. Among other factors, infection with hepatitis B may be the single most important factor for development of this carcinoma.1,2
According to the CDC, the hepatitis B vaccine is recognized as the first anti-cancer vaccine because it can prevent primary liver cancer.3
A clear link has been demonstrated between chronic hepatitis B infection and the occurrence of hepatocellular carcinoma. In a Taiwanese study, the institution of universal childhood immunization against hepatitis B virus has been shown to decrease the incidence of hepatocellular carcinoma among children.4 In a Korean study in adult males, vaccination against hepatitis B virus has been shown to decrease the incidence of, and risk of, developing hepatocellular carcinoma in adults.5
Considering the serious consequences of infection, immunization should be considered for all persons at potential risk of exposure to the hepatitis B virus. Mothers infected with hepatitis B virus can infect their infants at, or shortly after, birth if they are carriers of the HBsAg antigen or develop an active infection during the third trimester of pregnancy. Infected infants usually become chronic carriers. Therefore, screening of pregnant women for hepatitis B is recommended.1 Because a vaccination strategy limited to high-risk individuals has failed to substantially lower the overall incidence of hepatitis B infection, the Advisory Committee on Immunization Practices (ACIP) recommends vaccination of all persons from birth to age 18.6 The Committee on Infectious Diseases of the American Academy of Pediatrics (AAP) has also endorsed universal infant immunization as part of a comprehensive strategy for the control of hepatitis B infection.7 The AAP, American Academy of Family Physicians (AAFP), and American Medical Association (AMA) also recommend routine vaccination of adolescents 11 to 12 years of age who have not been vaccinated previously.8 The AAP further recommends that providers administer hepatitis B vaccine to all previously unvaccinated adolescents.9 (See INDICATIONS AND USAGE.) There is no specific treatment for acute hepatitis B infection. However, those who develop anti-HBs antibodies after active infection are usually protected against subsequent infection. Antibody titers ≥10 mIU/mL against HBsAg are recognized as conferring protection against hepatitis B.1 Seroconversion is defined as antibody titers ≥1 mIU/mL.
Protective efficacy with ENGERIX-B has been demonstrated in a clinical trial in neonates at high risk of hepatitis B infection.10,11 Fifty-eight neonates born of mothers who were both HBsAg and HBeAg positive were given ENGERIX-B (10 mcg at 0, 1, and 2 months) without concomitant hepatitis B immune globulin. Two infants became chronic carriers in the 12-month follow-up period after initial inoculation. Assuming an expected carrier rate of 70%, the protective efficacy rate against the chronic carrier state during the first 12 months of life was 95%.
Immunization with 10 mcg at 0, 1, and 6 months of age produced seroconversion in 100% of infants by month 7, with a geometric mean antibody titer (GMT) of 713 mIU/mL (N = 52), and the seroprotection rate was 97%.
Clinical trials indicate that administration of hepatitis B immune globulin at birth does not alter the response to ENGERIX-B.
Immunization with 10 mcg at 0, 1, and 2 months of age produced a seroprotection rate of 96% in infants by month 4, with a GMT among seroconverters of 210 mIU/mL (N = 311); an additional dose at month 12 produced a GMT among seroconverters of 2,941 mIU/mL at month 13 (N = 126).
In clinical trials with 242 children aged 6 months to, and including, 10 years given 10 mcg at months 0, 1, and 6, the seroprotection rate was 98% 1 to 2 months after the third dose; the GMT of seroconverters was 4,023 mIU/mL.
In a separate clinical trial including both children and adolescents aged 5 to 16 years, 10 mcg of ENGERIX-B was administered at 0, 1, and 6 months (N = 181) or 0, 12, and 24 months (N = 161). Immediately before the third dose of vaccine, seroprotection was achieved in 92.3% of subjects vaccinated on the 0-, 1-, and 6-month schedule and 88.8% of subjects on the 0-, 12-, and 24-month schedule (117.9 mIU/mL versus 162.1 mIU/mL, respectively, P = 0.18). One month following the third dose, seroprotection was achieved in 99.5% of children vaccinated on the 0-, 1-, and 6-month schedule compared to 98.1% of those on the 0-, 12-, and 24-month schedule. GMTs were higher (P = 0.02) for children receiving vaccine on the 0-, 1-, and 6-month schedule compared to those on the 0-, 12-, and 24-month schedule (5,687.4 mIU/mL versus 3,158.7 mIU/mL, respectively). The clinical relevance of this finding is unknown.
In clinical trials with healthy adolescent subjects 11 through 19 years of age, immunization with 10 mcg using a 0-, 1-, and 6-month schedule produced a seroprotection rate of 97% at month 8 (N = 119) with a GMT of 1,989 mIU/mL (N = 118, 95% confidence intervals = 1,318-3,020). Immunization with 20 mcg using a 0-, 1-, and 6-month schedule produced a seroprotection rate of 99% at month 8 (N = 122) with a GMT of 7,672 mIU/mL (N = 122, 95% confidence intervals = 5,248-10,965).
Clinical trials in healthy adult and adolescent subjects have shown that following a course of 3 doses of 20 mcg ENGERIX-B given according to the ACIP-recommended schedule of injections at months 0, 1, and 6, the seroprotection (antibody titers ≥10 mIU/mL) rate for all individuals was 79% at month 6 and 96% at month 7; the GMT for seroconverters at month 7 was 2,204 mIU/mL. On an alternate schedule (injections at months 0, 1, and 2) designed for certain populations (e.g., neonates born of hepatitis B–infected mothers, individuals who have or might have been recently exposed to the virus, and certain travelers to high-risk areas. See INDICATIONS AND USAGE), 99% of all individuals were seroprotected at month 3 and remained protected through month 12. On the alternate schedule, an additional dose at 12 months produced a GMT for seroconverters at month 13 of 9,163 mIU/mL.
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