Fifty-two adults who had previously received 4 x 20 mu g doses of hepa
titis B [Engerix-B] vaccine (appropriately administered into the delto
id muscle) and who had failed to develop detectable anti-HBs were rand
omized to receive a fifth dose of Engerix-B (either 20 lug or 40 mu g)
intramuscularly (deltoid). The participants were blinded as to the co
ntents of the syringe. Anti-HBs was tested (by EIA) 3 months after the
injection. Anti-HBs results from 45 non-responders were evaluable. Se
ven vaccinees were excluded; four of these on the basis of failure to
have follow-up blood collected and three who were found to be anti-HBc
positive (one HBsAg positive). Twelve of 22 (54.5%) of those receivin
g 20 mu g of HB vaccine developed anti-HBs, whereas 10 of 23 (43.5%) w
ho received 40 mu g developed anti-HBs, showing no significant differe
nce between the regimens. The mean geometric titres were 93 +/- 50 and
86 +/- 51 IU l(-1), respectively. Vaccinee groups were well matched f
or age, sex and body mass index and the interval between injection and
bleeding. Side-effects in those receiving the double (40 mu g) dose w
ere no different from those receiving the normal (20 mu g) adult dose.
On the basis of this study, a fifth dose of vaccine in non-responsive
vaccinees is recommended. No significant advantage of 40 mu g over 20
mu g of vaccine was observed. Whilst smoking and obesity were common
in this cohort of non-responders and probably contributed to the indiv
iduals primary non-responsive state, these factors had no unfavourable
effect on response to a fifth dose of vaccine. (C) 1997 Elsevier Scie
nce Ltd.