Efficacy of hepatitis B immunization with reduced intradermal doses

Intradermally (I.D.) administered reduced doses of HB-Vax and Hevac-B were tested against the standard protocols for administering these two vaccines. Immunogenicity, efficacy and possible side effects were evaluated.Four-hundred-sixty-two healthy subjects were vaccinated as follows: Fifty-two subjects received HB-Vax and 99 Hevac B according to the standard regimens. The remaining subjects received 3 I.D. injections in the deltoid region at one-month intervals in the following doses: 165 subjects with 2 g doses of HB-Vax, 118 subjects with 1 ug doses of Hevac-B and 28 subjects with 0.5 g (minimal) doses of Hevac-B. Post-vaccination tests (anti-HBs titres and other serological markers for HBV) were to be performed 30, 60, 90, 180, 270 and 360 days after the first injections.Side effects seen with the experimental protocols were acceptable and limited to local reactions. It was found that, on the whole, reduced I.D. doses of both vaccines produced very high immune responses showing a consistently greater efficacy than those of the standard protocols, though the differences were not always statistically significant.Ninety days after the first injections, 80.8% and 82.7% of subjects vaccinated with reduced I.D. doses of HB-Vax showed seroconversion as opposed to only 62.0% of those receiving standard protocol HB-Vax.Seroconversion rates at 90 days in subjects receiving reduced I.D, doses of Hevac-B were 92.0% and 87.996 and for those receiving the minimal doses of this vaccine, 94.1% The rate of seroconversion obtained with standard administration of Hevac-B was 83.8%. The antibody titres in the experimental groups tended to increase up to the 180th day and were generally higher than those obtained with standard protocols. The titres remained very high 270 days after the first injection.Corresponding author.