Dose range study in healthy volunteers of a hepatitis B vaccine produced in yeast

Safety and immunogenicity of hepatitis B vaccine ButaNG in adults

Recombinant yeast-derived hepatitis B vaccine manufactured by Instituto Butantan was administered in two groups of adult volunteers (I, II) following two different schedules of immunization. In the first trial (10 &mgr;g doses and 0, 1, 3 months vaccination schedule) 106 individuals completed the full immunization program. The results of seroconversion by age group varied from 70 to 100% and the GMT from 46.5 to 124.9 mIU mL-1. In the second trial with 68 individuals (for dosage comparison and 0, 1, 6 months vaccination schedule) indicated that the vaccine formulated in 20 &mgr;g was more effective than in 10 &mgr;g. The adverse reactions observed in the vaccinees were less frequent than the ones previously found since the introduction of similar vaccines.

Preliminary report of the use on adults of a recombinant yeast-derived hepatitis B vaccine manufactured by Instituto Butantan

Three 10 micrograms of the recombinant hepatitis B vaccine, manufactured by Instituto Butantan by original technology, were administered in an adult population, mean age 30 years old, following the 0, 1 and 6 months schedule immunization. The clinical trial was considered satisfactory in terms of immunogenicity (anti-HBs titers between 17.5-29500 IU/ l, seroconversion 95.3%) and reactogenicity (no incapacitating side effects).

Accelerated Schedule for Hepatitis B Immunization

Background: A considerable number of people remain unprotected against hepatitis B. These people may require immunization at short notice before being exposed to situations or locations where a risk of infection is present. Currently, full active immunization against hepatitis B, when administered according to recommended schedules, takes 2-6 months. This open, randomized multicentric study evaluated the reactogenicity and immunogenicity of a recombinant hepatitis B vaccine in adults when it was administered according to three different rapid vaccination schedules. Methods: Five hundred and twenty four healthy adults (aged 18-59 years) were randomly divided into three groups. Hepatitis B vaccine was given intramuscularly in the deltoid muscle at months 0, 1, and 2 (group A); weeks 0, 14, and 28 (group B); and weeks 0, 7, and 21 (group C). Symptoms were recorded by the subjects on individual diary cards. AntiHBs were measured using radioimmunoassay (Ausab-Abbott); a seroprotective titer was defined as 10 IU/L. Results: At day 28, no significant difference in seroprotection rates (SPRs) i.e., seroconversion >= 10 IU/L,was observed, between groups B (55.6%) and C (65.2%), but both these groups had significantly greater SPRs than group A (15.0%). Although not significant (p=.07), groups B and C also had higher SPRs than group A (78.5% and 76.4% versus 65%) at day 56. One month after completing the three dose schedules, the SPRs were as follows: 89.0% (group A); 78.5% (group B); and 76.4% (group C), increasing to > 94% at month 7 to 8 in all three groups. The SPRs at month 13 were 95.8%, 98.9%, and 98.6%, respectively. Among the three groups, no significant differences were observed from month 2 onwards in either SPRs or geometric mean titers. In groups A, B, and C, 3.7%, 5.0%, and 7.1% of the vaccine injections were associated with local symptoms. Also 8.3%, 6.2%, and 6.3% of subjects exhibited general symptoms following each vaccine dose; all symptoms were transient and resolved spontaneously. Conclusions: This recombinant hepatitis B vaccine administered at weeks 0, 7, 21, or at weeks 0, 14, 28, rapidly elicits high rates of seroprotection, which persist at least until month 12.

Comparison of immunogenicity of recombinant and plasma derived hepatitis B antigen in guinea-pigs

Four different preparations of hepatitis B antigen (HBsAg) were tested in parallel with respect to their ability to elicit anti-HBs in guinea-pigs. We compared the effect of low doses (5 micrograms single dose and 30 micrograms total amount) of human plasma derived and recombinant HBsAg, in purified forms or prepared as vaccines, respectively. The highest titre of anti-HBs developed was detected in guinea-pigs immunized with plasma derived HBsAg, followed the by response in animals immunized with plasma derived vaccine. Purified recombinant antigen and recombinant vaccine exhibited poor immunogenicity compared with plasma derived antigen preparations. The increase in the dose of recombinant antigen (150 micrograms total amount) resulted in markedly improved response in two out of ten animals. Anti-HBs immunoglobulin fractions from pooled sera within each group of animals were isolated, partially purified, coupled to polystyrene beads and subsequently used in immunoradiometric assay with monoclonal 125I-anti-HBs. Only the anti-HBs isolated from pooled sera of animals immunized with purified plasma derived antigen met the requirements for high sensitivity and antigen specificity in such assay. Comparable properties were exhibited by the anti-HBs obtained from one guinea-pig immunized with a larger amount of recombinant antigen. With these two anti-HBs immunoglobulin preparations, amounts as low as 1 ng of HBsAg could be detected.

A new vaccine against tick-borne encephalitis: initial trial in man including a dose-response study

A new vaccine against tick-borne encephalitis was investigated in 56 healthy volunteers randomized for five different doses of antigen in a comparative group trial. Good tolerability and high immunogenicity were found using three different antibody test systems. The dose response study revealed that there was a strong relationship between the amount of antigen administered and the antibody response over the range of 0.03-3.0 micrograms antigen per dose.

Four-year experience with a recombinant hepatitis B vaccine

Three hundred and forty-three healthy adults were vaccinated with five different lots of recombinant hepatitis B vaccine. Three hundred and forty (99.1%) individuals produced antibodies against hepatitis B surface antigen (anti-HBs). Peak anti-HBs concentrations were significantly higher in females and younger individuals. All anti-HBs positive individuals developed antibodies to the common determinant "a" of HBsAg. The vaccine was well tolerated, without severe side reactions. Persistence of anti-HBs was followed in 130 individuals for 3, and in 15 for 4 years after the first vaccination of these two groups. 21.7% and 32.3%, respectively, no longer had protective levels of anti-HBs after this time. The persistence of anti-HBs was dependent on peak anti-HBs levels, with consistent kinetics of anti-HBs decline. Revaccination of individuals whose specific antibody levels had fallen below 10 IU/l led to a prompt anti-HBs response. Comparison with individuals vaccinated with plasma-derived hepatitis B vaccine revealed no substantial differences between the two vaccines.

Multicentre dose range study of a yeast-derived hepatitis B vaccine

Healthy young adult volunteers, 778 in number, without HBV markers were randomly distributed into groups and administered different lots of a yeast-derived hepatitis B vaccine (YDV) at different dose levels or a commercial plasma-derived vaccine (PDV), according to a 0, 1, 2, 12-month vaccination schedule. The YDV proved to be safe and well tolerated, even when partly purified lots were given. Reactions were mild and transient, comparable to those observed after PDV. One month after three YDV doses, 0-7% of subjects overall had failed to seroconvert; all those evaluated one month after the booster dose had seroconverted. No significant difference was found between the two vaccine types as far as seroconversion rates were concerned. Geometric mean anti-HBs levels following three vaccine doses were higher in seroconverters of the PDV groups. However, a booster dose of YDV resulted in high anti-HBs levels in all groups varying from 11,474 to 51,404 IU l-1 (purified YDV lot), 4915 to 18,832 IU l-1 (partly purified YDV lots) and 11,008 to 15,805 IU l-1 (PDV lots). Of seroconverters to the purified lots of YDV 93% attained 1000 IU l-1 after the booster dose, thus ensuring protection for a number of years. Dose-response studies provided a basis for the selection of 20 micrograms of highly purified YDV as the standard dose.

Immunogenicity of recombinant hepatitis B vaccine in dialysis patients

Eighty-eight dialysis patients were vaccinated with recombinant hepatitis B vaccine prepared in yeast. Fourty-nine patients were immunized 3 times (months 0, 1, 6) intragluteally with 40 micrograms hepatitis B surface antigen (HBsAg) per dose. Only 32 of them (65.3%) showed anti-HBs concentrations above 10 IU/l with a geometric mean titer (GMT) of 180.7 IU/l after 3 vaccinations, whereas all of the 16 healthy controls, vaccinated 3 times with a 10-micrograms dose of the same vaccine batch, had specific antibodies higher than 10 IU/l (GMT 897.4 IU/l). Responses of patients were slightly higher than those of dialysis patients vaccinated in an earlier study with plasma-derived vaccine according to the same schedule. Results in 20 patients immunized 6 times intragluteally with 40 micrograms HBsAg/dose in monthly intervals were not better (at month 7, 65% showed anti-HBs concentrations greater than 10 IU/l; GMT = 126.6 IU/l), and 19 patients receiving 6 times 20 micrograms HBsAg monthly showed significantly lower responses (anti-HBs greater than 10 IU/l in 42% of vaccinees, GMT = 89.5 IU/l). The vaccine was tolerated well; side-effects were slight, and no serious adverse reactions were observed. In conclusion, recombinant hepatitis B vaccine is comparable to plasma-derived vaccine also in the case of dialysis patients; a 6-dose schedule does not seem to have much advantage compared to the conventional 3-dose regimen.