S. Thoelen

Safety and immunogenicity of a hepatitis B vaccine formulated with a novel adjuvant system

A formulation of recombinant hepatitis B surface antigen (HBsAg) combined with a novel adjuvant system, SBAS4--a combination of aluminium salt and monophosphoryl lipid A (MPL), was assessed in 27 healthy adult volunteers with a commercial vaccine (Engerix-B) as control. After three doses (0, 1, 6 months schedule), reactogenicity profiles were similar. Local reactions were essentially mild, the most frequent being soreness at the injection site. Seroprotection was achieved after two doses in all subjects given the candidate vaccine, all Engerix-B vaccines being seroprotected after the third dose. After the second and third doses, higher anti-HBs Geometric Mean Titres (GMTs) were observed in the group which received the formulation with the novel adjuvant system, and cellular immunity, measured as HBsAg-specific lymphoproliferation was stronger than with Engerix-B. These results indicate that the new formulation is safe, well-tolerated and immunogenic and may promote more rapid protection against hepatitis B infection.

The first combined vaccine against hepatitis A and B: an overview

Hepatitis A and B infections are prevalent world-wide and are a significant cause of morbidity and mortality. A vaccine providing dual protection against hepatitis A and B is now available (Twinrix, SmithKline Beecham Biologicals). Six pivotal vaccine trials, involving 843 healthy adults, aged between 17 and 60 years and vaccinated following a 0, 1, 6 month schedule are discussed. At month 2 more than 99% of the vaccinees were seropositive for anti-HAV and 84% were protected against hepatitis B. The third dose induced a 12-fold increase in geometric mean titres (GMTs) to 5404 mIU/ml. One month after completion of the vaccination course nearly all vaccinees had protective titres against hepatitis B with a GMT of 4818 mIU/ml. Long term follow-up data until month 48 is available for two studies. At month 48 all 129 vaccinees sampled were still positive for anti-HAV antibodies and > 95% were still protected against hepatitis B. The combined hepatitis A and B vaccine Twinrix proves to be consistently safe, well tolerated and highly immunogenic and compares well with serological responses reached with monovalent vaccines. This combined hepatitis A and B vaccine offers more convenience, potentially better compliance and lower administration costs.

A hepatitis B vaccine formulated with a novel adjuvant system.

Although more than 95% of the vaccinated population responds to the currently licensed vaccines against hepatitis B, some groups were found to be low responders. Lipid A as adjuvant, through its ability to activate macrophages, might improve humoral as well as cellular immune response. Therefore we evaluated the profile of a hepatitis B vaccine with the new adjuvant system SBAS4. 150 young adults were enrolled and randomized into three groups: one received the SBAS4 hepatitis B vaccine, the second Engerix-B(TM) and the third a hepatitis B vaccine with an alternative formulation on alum. Vaccinations were at 0 and 6 months. The vaccine was well tolerated. At month 7 all vaccinees were protected but with significant differences in GMTs between groups: 13,271 mIU/ml for the SBAS4 group versus 1203 and 1823 mIU/ml. Hence the hepatitis B vaccine with the new adjuvant system is more immunogenic compared to the other vaccines containing the same antigen and could be suitable for a two dose schedule.

Two-Dose Combined Vaccination against Hepatitis A and B in Healthy Subjects Aged 11-18 Years

BACKGROUND In this open, randomized trial the safety, reactogenicity, and immunogenicity profile of a high-dose combined hepatitis A and B candidate vaccine was compared with that of Twinrix Paediatric in healthy volunteers aged 11-18 years. METHODS One hundred subjects were randomly allocated to either of two groups. One group received the high-dose vaccine (720 E1.U HAV antigen; 20 microg hepatitis B surface antigen (HBsAg) at months 0 and 6; the second group received Twinrix Paediatric (360 E1.U HAV antigen; 10 microg HBsAg), following a 0-1-6-month schedule. RESULTS Injection site soreness and fatigue were the most frequently reported solicited symptoms. For hepatitis A all subjects had seroconverted at month 7, and geometric mean titres (GMT) were 8,151 mIU/ml in the high-dose group and 6,394 mIU/ml in the Twinrix Paediatric group. For hepatitis B the GMT for the Twinrix Paediatric group was significantly higher at month 2 and month 6. However, no difference in GMT between groups could be established at month 7. The seroprotection rate attained 100% in both groups, and GMT were 4,212 mIU/ml (high-dose group) and 6,330 mIU/ml (Twinrix Paediatric). CONCLUSIONS The two vaccines showed similar safety and reactogenicity profiles. After completion of the vaccination schedule, no difference in immunogenicity was shown. This high-dose vaccine, administered following a two-dose schedule, can be considered an alternative regimen for the immunization of healthy adolescents against hepatitis A and hepatitis B infections, in a setting where vaccinees are not immediately at risk of exposure to hepatitis B.

Comparison of the reactogenicity and immunogenicity of a two injection combined high-dose hepatitis A and hepatitis B vaccine to those of Twinrix.

Twinrix (SmithKline Beecham Biologicals) is a combined hepatitis A and B vaccine licensed with a three-dose schedule. A two-dose combined hepatitis A and B vaccine would facilitate immunisation programs. In this prospective study, 100 healthy adults, aged between 18 and 40, were enrolled. A first group of 50 was given a high-dose vaccine at month 0 and 6. A second group of 50 received Twinrix at month 0, 1 and 6. The reactogenicity was assessed after each vaccine dose. There were no severe local adverse events. Seven severe systemic reactions occurred, of which five were fatigue, one was headache and one consist in gastrointestinal symptoms. They all resolved during the 4-day follow-up period. One serious general adverse event was reported, but was clearly unrelated to the vaccine. Thus, both vaccines were well tolerated. The immunogenicity was evaluated by testing for anti-HBs and anti-HAV antibodies. Seroconversion rates and geometric mean titres (GMTs) were compared. At month 7, the anti-HAV GMTs were higher in the high-dose group than in the Twinrix group and, inversely, the anti-HBs GMTs were slightly higher in the Twinrix group than in the high-dose group. At month 7, all subjects in both groups were positive for anti-HAV. All subjects in the high-dose group and 97.6% subjects in the Twinrix group had seroconverted for anti-HBs. Therefore, it can be concluded that with two injections of the high-dose hepatitis A and B vaccine, 6 months apart, a similar immune response can be obtained as induced with three doses of Twinrix at months 0, 1 and 6.

Reactogenicity and immunogenicity of a combined hepatitis A and B vaccine in healthy adults

A safe and effective vaccine for hepatitis A and B together, would be very beneficial in preventing morbidity of both infections, particulary in high risk groups. The objectives of this trial are to assess the reactogenicity and to evaluate the immunogenicity of a combined hepatitis A and B vaccine. Forty-nine adult volunteers were vaccinated intramuscularly at month 0, 1, and 6, with a combined vaccine containing 720 Elisa Units hepatitis A antigen (killed) and 20 μg hepatitis B antigen (yeast-derived), prepared by SB Biologicals. Anti-HAV antibodies, anti-HBs antibodies and liver enzymes were measured at month 1, 2, 6, and 7 and are planned at months 18 and 24. Seroprotection for hepatitis B was 89.6% (43/48) at month 6, and reached 100% (48/48) at month 7. The geometric mean titers (GMTs) are 58IU/1 and 1305IU/1 respectively. At month 6,100% (48/48) of the subjects had a protective antibody titer for hepatitis A. The administration of the booster dose results in a greater than 10-fold increase of GMT for anti HAV-titers (from 459 IU/1 to 5368 IU/1). The combined vaccine is well tolerated and safe. It induces high levels of neutralizing antibodies for HAV and good levels of antibodies for HBV. This candidate vaccine looks promising for individuals at risk for both infections: travelers, military personnel, and health care workers.