COMPARISON OF 2 IMMUNIZATION SCHEDULES WITH RECOMBINANT HEPATITIS-B VACCINE AND NATURAL IMMUNITY ACQUIRED BY HEPATITIS-B INFECTION IN DIALYSIS PATIENTS

In a prospective study over a 2-year period we compared two practical dosage schedules to vaccinate dialysis patients against hepatitis B vi rus (HBV) infection using a yeast-derived recombinant hepatitis B vacc ine (Engerix-B). In addition, the natural history of this acquired imm unity was compared with that developed through HBV infection in dialys is patients and healthy subjects. Patients on dialysis treatment (haem o or peritoneal) who were tested to be negative for hepatitis B surfac e antigen (HBsAg), anti-HBs and anti-HB core were allocated at random to receive HB vaccine according to one of the two schedules. The two g roups receiving the vaccine were matched for age, sex, mean duration o n dialysis and the form of dialysis treatment received. The group of p atients who received a four-dose schedule tar 0, 1, 2 and 6 months) of 40 mu g of HB vaccine each time (group 2) achieved a seroconversion r ate of 79% 1 month after the last dose (at month 7) compared with a se roconversion rate of 55% in those who received three doses (at 0, I an d 6 months) of 40 mu g each (group I). Healthy controls who received h alf the amount of vaccine on a three-dose schedule (group 3) attained 100% seroconversion (p < 0.05). When retested at 24 months, 30% of ser oconverters in group I had lost their protective immunity, compared wi th only 6% in group 2 and 15% in group 3. The magnitude of antibody re sponse (total and anti-(a)-specific) was assessed in the vaccinees at 24 months and compared with that of two other control groups, dialysis patients (group 4) and healthy volunteers (group 5), who had acquired immunity from HBV infection. In general, the total and anti-(a)-speci fic HBs titres in the dialysis patients (groups 1, 2 and 4) were lower than in their corresponding healthy controls (groups 3 and 5), irresp ective of whether the protective immunity was acquired by vaccination or HBV infection. However, the anti-HBs titres in dialysis patients wh o received four doses were significantly higher than in those who rece ived only three doses (p < 0.05), which indicated a better protective immunity in favour of the former regime. The magnitude of antibody res ponse in the vaccinees of groups 2 and 3 compared well with their resp ective controls, groups 4 and 5, who had acquired their immunity throu gh HBV infection. This implied that the yeast-derived vaccine was suff iciently immunogenic and provided lasting protection in patients and h ealthy subjects vaccinated by an appropriate dosage schedule. When the different factors that could have influenced the outcome of vaccinati on in dialysis patients were analysed, the elderly and patients with d iabetes were found to be at a disadvantage. In conclusion, the study s upports the use of a 40 mu g-four-dose schedule to vaccinate dialysis patients with HB vaccine as it provides immune protection to an accept able proportion of vaccinated subjects and this lasts for 24 months in almost all seroconverters. The magnitude of antibody response is comp arable to that acquired by dialysis patients following HBV infection.