There are observations in nature which indicate that antibody against the surface antigen is protective. In their early studies, Okochi and Murakami observed that transfused patients with antibody were much less likely to develop hepatitis than those without it. I n a long term study, London has shown that patients on a renal dialysis unit, and the staff who served them, were much less likely to develop hepatitis if they had antibody then if they did not (Fig. 4). Edward Lustbader has used this data to develop a statistical method for rapidly evaluating the vaccine.