To the Editor.
—In response to an editorial1 that criticized the choice of 10 μg of yeast-derived hepatitis B surface antigen (HBsAg) as the dose for Recombivax-HB, Drs Gerety and Ellis2 seek to justify the decision to use a lower dose of HBsAg than the 20 μg present in the plasma-derived Heptavax-B vaccine. They minimize the quantitative difference that has been clearly demonstrated3 in the immune response to yeast-derived and plasma-derived hepatitis B vaccines manufactured by Merck Sharp & Dohme. In support of their argument, Drs Gerety and Ellis make reference to the published abstract4 of a presentation that I made at the recent International Symposium on Viral Hepatitis and Liver Disease and state that the "article indicates that therapy with either 10 μg of Recombivax-HB or 20 μg of another yeast-derived vaccine produces comparable antibody response."The fact is, the abstract and my presentation gave