Recombinant hepatitis B vaccine: a review of its immunogenicity and protective efficacy against hepatitis B.
Recombinant hepatitis B vaccine Engerix B((R)) [Hep-B(Eng)] is a noninfectious subunit hepatitis B viral vaccine indicated for the active immunisation of adults, children and infants against hepatitis B virus infection. It contains hepatitis B surface antigen (HBsAg) which is produced by the yeast Saccharomyces cerevisiae by use of recombinant DNA technology. In adults and children seroprotection rates [anti-HBsAg antibody (anti-HBs) titres >or=10 IU/L] were 93 to 100% 1 month after completion of the immunisation schedule with Hep-B(Eng) [0, 1, 6-month schedule]. A more rapid immunological response has been reported with accelerated Hep-B(Eng) immunisation schedules, such as the 0, 1, 2, 12-month schedule. Hep-B(Eng) produces seroprotection rates similar to those achieved with the plasma-derived vaccines and the recombinant hepatitis B vaccine, Recombivax-HB((R)) [Hep-B(Rax)] when administered at recommended doses. In studies in Taiwanese and Thai neonates born to hepatitis B carrier mothers, seroprotection rates were >or=94% 12 months after immunisation with Hep-B(Eng) [+/- hepatitis B immunoglobulin (HBIG)] and protective efficacy was high, with <or=4% of neonates becoming chronic hepatitis B carriers. Similarly, among 119 homosexual men, none had any markers of hepatitis B infection 1 month after completion of immunisation with Hep-B(Eng). Immunoprophylaxis with Hep-B(Eng) +/- HBIG compared with no immunoprophylaxis also resulted in a lower incidence of acute symptomatic hepatitis B infection among healthcare workers accidentally exposed to HBsAg-positive blood (0 vs 6%). Although seroprotective levels of anti-HBs have been reported to persist for at least 5 years in adults and 8 years in children immunised with Hep-B(Eng), anti-HBs titres do decline with time and may become undetectable several years after immunisation in some vaccinees. Moreover, it is currently unclear whether vaccinees require booster doses or whether, on exposure to the virus, natural boosting occurs when anti-HBs titres fall below the protective level (<10 IU/L). Long term follow-up studies should clarify this issue. Hep-B(Eng) is generally well tolerated with a tolerability profile similar to that of Hep-B(Rax) and plasma-derived vaccines. Mild soreness at the injection site is the most common adverse event associated with Hep-B(Eng).


CONCLUSIONS
Although further long term follow-up is necessary to determine the persistence of protective immunity against hepatitis B, available data indicate that Hep-B(Eng) is an effective and suitable alternative to other vaccines currently used for immunisation against infection caused by hepatitis B virus.
Adkins
J C
JC
Adis International Limited, Auckland, New Zealand. demail@adis.co.nz
Wagstaff
A J
AJ