Efficacy of CHO cell derived hepatitis B vaccine in children and adults.

The availability of hepatitis B vaccine and its incorporation in the EPI has reduced the frequency of HBV infection in most developed and developing countries. Two kinds of recombinant hepatitis B vaccines are available, one is derived from yeast and the other from CHO cells 1 . There arc three forms of HBsAg that are expressed in hepatitis B vaccine, namely the major form consisting of S protein alone, the large form containing the pre S-I and pre S-2 components and a middle form containing Pre S2-S components. The presence of these conform to the immunogenicity of the vaccine. All yeast derived vaccines contain only S antigen protein while CHO cell derived variety contains all three HBsAg forms i.e., the S protein, the pre S-I and pre S-2 antigen making its efficacy better than the other yeast derived or plasma derived vaccines. The present study was done to see whether low dose hepatitis B vaccination using CHO derived vaccine is able to produce sufficient immunity in Pakistani subjects.