0Original Report
Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in healthy Chilean subjects
V. Prado,(1) S. Riedemann/2) H. Ibarra/3' and M. Pbtin<4>
Objectives: A combination vaccine against hepatitis A and B provides the opportunity for simultaneous protection against both diseases with a single vaccine. This clinical study investigated the reactogenicity and immunogenicity of a combined hepatitis A and B vaccine (Twinrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) in healthy Chilean adults between 18 and 40 years of age.
Methods: In total, 345 healthy, seronegative health care workers were enrolled and randomized to three groups who received one of three lots of Twinrix on a 0-, 1- and 6-month schedules. Blood samples were screened 1 month after each dose for anti-HAV and anti-HBs antibodies. Reactogenicity after each dose was assessed using diary cards.
Results: The nature and incidence of symptoms were similar to those reported for other Twinrix studies. Very few symptoms were scored as severe. Upon completion of the vaccination, all subjects had anti-HAV antibodies with titers >6000 mlU/mL, and all but one were protected against hepatitis B, with titers >4000 mlU/mL.
Conclusions: We have demonstrated the high immunogenicity and tolerance of the combined hepatitis A and B vaccine. Combined vaccination has the advantage of offering dual protection with a reduction in the number of injections needed, lower associated costs, and a positive impact on compliance.
Int J Infect Dis 2002; 6: 129-133
INTRODUCTION
The hepatitis A and B viruses continue to cause serious morbidity and mortality throughout the world. In Latin America, there is evidence that the epidemiology of hepatitis A virus (HAV) is shifting from a high to an intermediate endemicity, with the population susceptible to HAV infection changing from children to adolescents and adults.1 In Chile, a recent study demonstrated a progressive increase in the number of susceptible school-age children of medium and low income in Santiago.2 A study conducted in Valdivia, Chile, among children from different socio-economic backgrounds, showed an inversely proportional correlation between socio-economic level and seroprevalence of anti-HAV antibodies.3 A similar study in the same region, among adults, confirmed this finding.4
There are an estimated 6 million hepatitis B (HBV) carriers in Latin America, with higher numbers in the north of Latin America.5 In Chile, the prevalence of
(1 'Departamento de Microbiología, Unidad Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile; <2>Instituto de Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; <3)Instituto de Medicina, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile;M'GlaxoSmithKline Biologicals, Chile.
Address correspondence to Dr. Valeria Prado, Departamento de Microbiología, Unidad Oriente, Facultad de Medicina, Universidad de Chile, Condell 303, Santiago, Chile. E-mail: vprado@machi.med.uchile.cl.
Corresponding Editorial Office: New York
HBV in the general population amounts to 0.6% against hepatitis B core antigen and is among the lowest in Latin American countries.6-8 Although some high-risk groups in Chile have been reported as having higher rates of HBV infection, in one study in Santiago, 5.916.1% of a group of health care personnel had at least one HBV marker (R. Tapia, personal communication), as did 21 % in another study of health care personnel.9
Protection against hepatitis B in high-risk groups is clearly favorable from a cost-benefit point of view.10 In the scenario of an epidemiologic shift of hepatitis A in Chile, young children and adolescents could also benefit from prevention through vaccination.
With regard to infections caused by hepatitis C virus (HCV), the prevalence and the frequency of serotypes vary in different regions of the world. Chile is a country with low prevalence, as demonstrated by the 0.14-0.3% seropositivity range obtained from voluntary blood donors in several studies conducted in Santiago de Chile.10
Active immunization against hepatitis A and hepatitis B diseases has been available for some time,1214 and both vaccines have proven to be effective and safe.15-17 Although both viruses are very different and their modes of transmission differ,18 a considerable similarity in epidemiologic aspects warrants combined hepatitis A and B vaccination. Infection by either the hepatitis A or B viruses is noticeably more prevalent in specific population groups, such as young adolescents and health care workers, where high-risk behavior is defined by lifestyle or occupation.2-819 Many of these groups that have been shown to be at high risk of
infection for both viruses would thus benefit from combined vaccination. One target group comprises young adolescents before they become sexually active, start traveling or engage in other risk behavior. At continuous risk of infection are health care personnel (mainly HBV)2o,2i and the staff of daycare centers (HAV).22-23 People who frequently receive blood-derived products, or are on dialysis, have long been known to be at risk for hepatitis B infection, but recent studies have shown that they might also be at risk for hepatitis A infection.24"26 Superinfection of hepatitis A in patients with chronic hepatitis B, hepatitis C or miscellaneous chronic liver disease increases the risk of fulminant hepatic failure or hepatocellular carcinoma.27-29
Combined vaccination reduces the number of interventions, and offers greater convenience and logistic advantages compared with immunization with the monovalent vaccines. This clinical trial investigated the reacto-genicity and immunogenicity of three different lots of combined vaccine against hepatitis A and B (Twinrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) in healthy Chilean adults between 18 and 40 years of age.
MATERIALS AND METHODS Vaccine
Three different lots of combined hepatitis A/hepatitis B vaccine (group 1 lot HAB102D6, group 2 Lot HAB123B6, and group 3 lot HAB103B6) containing at least 720 ELISA Units of hepatitis A antigen and 20 |ig of hepatitis B surface antigen were adsorbed onto 0.45 mg of aluminum in a total volume of 1 mL. Each dose of vaccine also contained 2-phenoxyethanol as a preservative.
Study participants
The trial was performed in two study centers, one at Departamento de Microbiología, Unidad Oriente, Faculty of Medicine, University of Chile in Santiago, and one at the University Austral of Chile in Valdivia. All protocols were approved by the Ethical Committees of both universities, and the studies were conducted in accordance with the Declaration of Helsinki and its amendments, taking in account Good Clinical Practice standards. The studies were initiated in June 1997 and completed in April 1998. All subjects gave written informed consent. Only health care workers were included (physicians, medical interns, nurses, dental students, and laboratory technicians). All subjects had to be seronegative for HAV antibodies, for hepatitis B surface (anti-HBs) and hepatitis B core (anti-HBc) antibodies, and negative for HBs Ag at the time of enrolment. All subjects were tested for the liver enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) prior to enrolment. Subjects with elevated serum liver enzymes (two-fold normal value of
45 U/L for ALT and 40 U/L for AST) were excluded. Also, subjects with a personal history of chronic liver disease, or other significant and persistent illness, or treated with any chronic medication, were excluded from the study.
Study design
This was a double-blind randomized study. Study vaccines (each containing 720 EL.U of hepatitis A antigen and 20 (ig of hepatitis B surface antigen, respectively) were administered according to 0-, 1- and 6-month schedules. The subjects were vaccinated intramuscularly in the deltoid region. Blood samples were obtained on the day of screening and at months 1,2,6 and 7.
To evaluate reactogenicity, all subjects were asked to complete symptom sheets for 4 days, starting on the day of vaccination. Solicited local reactions were soreness, redness and swelling, and general symptoms were fever, headache, malaise, fatigue, nausea and vomiting. Redness and swelling were scored as grade 1 (1 to <30 mm), grade 2 (>30 mm), and grade 3 (>30 mm and persisting for more than 24 h). Fever was graded as 1 (37.5-38.0°C), 2 (>38.0-39.0°C) and 3 (>39.0°C). All other local and general symptoms were scored as 1 (adverse experience easily tolerated), 2 (adverse experience sufficiently discomforting to interfere with daily activities), and 3 (adverse experience which prevents normal everyday activities). Adverse events were reported up to 30 days following vaccination, and serious adverse events were reported during the whole study period.
Serology
Serum liver enzymes (AST and ALT) were tested at Laboratorio de Especialidades Médicas, Santiago, Chile. Anti-HAV antibodies were measured by screening at Laboratorio de Gastroenterologia del Hospital Clinico de la Universidad de Chile and Instituto de Microbiología, Facultad de Ciencias, Universidad Austral de Chile. The test used was a commercially available enzyme immunoassay kit (HAVAB EIA: Abbott Labortories, Abbot Park, IL, USA). Subsequent testing was done with the Enzymum Boehringher kit (Boehringer Mannheim, Mannheim, Germany) at GlaxoSmithKline Biologicals laboratory. The cutoff level of this test is 33 mlU/mL. Therefore, subjects with antibody titers >33 mlU/mL are considered to be seropositives. Seroconversion was defined as cases of negative antibody titers who increased to a titer >33 mlU/mL. Anti-HBs antibodies were measured using a commercial RIA test (AUSAB, Abbott)at Laboratorio de Gastroenterologia del Hospital Clinico de la Universidad de Chile and Instituto de Microbiología, Facultad de Ciencias, Universidad Austral de Chile. Subjects with an anti-HBs antibody titer below 1 mlU/mL were considered to be seronegative. An increase to > 1 mlU/mL was con-
sidered a seroconversion, and titers > 10 mlU/mL were considered to be seroprotective.
Statistics
A descriptive analysis was performed for the reactogenicity and the immunogenicity, with calculation of geometric mean titers (GMTs) and 95% confidence intervals using the SAS statistical package. Randomization was done using an algorithm of pseudorandom numbers and a randomization blocking scheme (1:1:1).
RESULTS
Enrolment and study attrition
In total, 345 subjects were enrolled, of whom 115 were allocated to each study group. Screening for anti-HAV (total antibodies) and anti-HBV (anti-HB core, anti-HBs and HBs Ag) was performed. In total, 763 subjects were tested for anti-HAV (468 in Santiago and 295 in Valdivia) in order to obtain the 345 seronegatives planned to be enrolled. In Santiago, 238/468 (51%) of the subjects tested were anti-HAV positive, and in Valdivia, 158/295 (53.6% )were anti-HAV positive. Of 468 subjects screened for HBV, only six were positive for any of the markers. One subject was withdrawn for having elevated AST levels at the time of the first dose. Later blood tests showed normal transaminase levels. A further nine subjects were excluded from the ATP analysis for immunogenicity because of blood sampling or vaccination timings outside the protocol specifications, one subject because of being under the required age, four because they had taken medication not foreseen in the protocol, and one because of an adverse event unlikely to be related to vaccination (see below); three were dropped from the analysis because they had abnormally high antibody titers after the first vaccination.
Demographics
Overall, the mean age was 22.6 years. There were 56.8% females (mean age 22.6 years) and 43.2% males (mean age 22.6 years). Gender composition and mean ages were similar for all three study groups.
Reactogenicity
We report data from 1029 doses documented on diary cards. The incidence and nature of the symptoms were similar for all three groups (lots). Local symptoms were more frequently reported than general symptoms. A detailed analysis is presented in Table 1. Injection site soreness was the most reported local symptom, and headache the most frequently encountered general symptom. Very few symptoms were scored as severe.
Table 1. Incidence of local and general symptoms
N Group 1 342 Group 2 342 Group 3 344
Local3
Redness All 31.0 33.6 34.9
Grade 3 0 0 0
Soreness All 60.2 60.2 61.9
Grade 3 0 0.3 0.3
Swelling All 16.1 17.3 18.6
Grade 3 0 0 0
General3
Fatigue All 14.0 21.6 15.4
Grade 3 0 0.3 0.3
Fever All 3.8 4.1 6.4
Grade 3 0 0.3 0
Headache All 23.4 28.7 24.1
Grade 3 1 1 0.6
Nausea All 3.5 7.9 4.7
Grade 3 0 2.0 0
Vomiting All 0.9 1.5 0.3
Grade 3 0 0.3 0
Expressed in %.
Over the course of the study, 161 subjects (61 in group 1, 54 in group 2, and 46 in group 3) reported at least one unsolicited adverse event during the 30-day follow-up period after each vaccine dose. In total, 272 unsolicited adverse events (99 in group 1,95 in group 2, and 78 in group 3) were reported. Overall, during the 30-day follow-up period after each dose, 259 doses (93 in group 1,93 in group 2, and 73 in group 3) were followed by at least one report of an unsolicited adverse event. Only six of these unsolicited events were local reactions (four reported as increased temperature at injection site, and two as local pruritus).
One serious adverse event was reported during this trial. Nine days after the first vaccination, a subject was hospitalized for erythema multiforme. The event occurred subsequent to oral antibiotic treatment for pharyngitis and tonsillitis, and was therefore determined by the investigator as unlikely to be related to vaccination. The subject recovered without sequelae.
Immunogenicity
Seropositivity rates and GMTs are presented in Table 2 (anti-HAV) and Table 3 (anti-HBV). Upon completion of the vaccination, all vaccinees had antibodies against hepatitis A and all but one subject were protected against hepatitis B. The rates of seroconversion and GMTs are very similar between all three groups (three different lots) included in the study.
DISCUSSION
This study investigated the reactogenicity and immunogenicity of three different lots of GlaxoSmithKline Biologicals combined vaccine (Twinrix) against hepatitis A and B. All three lots induce a satisfactory immune response in this healthy adult cohort, with similar results
Table 2. Anti-HAV immunogenicity
Anti-HAV response (titer > 33mlU/mL)
Groups Timing N % S+ GMT 95% Ci
1 M 1 106 95.5 444 372-530
M 2 110 99.1 1509 1247-1827
M 6 110 99.1 478 410-557
M 7 111 100 6072 5225-7056
2 M 1 108 99.1 506 417-614
M 2 109 100 1427 1184-1718
M 6 109 100 488 416-573
M 7 109 100 6669 5812-7652
3 M 1 106 100 465 377-573
M 2 106 100 1466 1192-1803
M 6 105 100 462 391-545
M 7 105 100 6475 5597-7489
Vaccination schedule 0, 1 and 6 months.
M 1, sample obtained 1 month after dose 1 of vaccine; M2, sample 1 month after dose 2; M6, sample before booster at month 6; M7, sample 1 month after booster; % S+, seropositivity rate (anti-HAV titer>33 mlU/mL); GMT, geometric mean titer; 95% CI, 95% confidence interval.
Table 3. Anti-HBV immunogenicity
Anti-HBV response (titer > 10 mlU/mL)
Groups Timing N % SP GMT 95% CI
1 M 1 111 31.5 9 7-14
M 2 111 80.2 65 45-93
M 6 111 95.5 167 125-223
M 7 111 100 4182 3170-5518
2 M 1 109 45.9 15 11-20
M 2 109 86.2 92 67-126
M 6 109 98.2 262 201-340
M 7 109 100 6329 4872-8220
3 M 1 72 34 11 8-16
M 2 102 84.9 86 61-122
M 6 104 95.2 197 148-260
M 7 105 99.0 4809 3416-6770
Vaccination schedule 0, 1 and 6 months.
M1, sample obtained 1 month after dose 1 of vaccine; M2, sample 1 month after dose 2; M6, sample before booster at month 6; M7, sample 1 month after booster; % SP, seroprotection rate (anti-HBs titers 10 mlU/mL); GMT, geometric mean titer; 95% CI, 95% confidence interval.
for all three lots. Comparing our data to those obtained with the combined hepatitis A and B vaccine in six pivotal clinical trials in 843 healthy subjects,30 we show that the seropositivity (for hepatitis A) and seroprotection rates(for hepatitis B) and GMTs (for hepatitis A and B) fall within the same range for both antigens. A study conducted with a monovalent hepatitis A vaccine in Valvidia showed similar high seroconversion rates for the anti-HAV component, but somewhat lower seroconversion rates than with the combined hepatitis A and B vaccine used in this study.31 The fact that higher anti-HAV titers are obtained with Twinrix compared to monovalent vaccination has been reported by other investigators.32
Similarly, the 99-100% seroprotection rate for the HBV response is noteworthy, since it is higher than that in previously conducted trials with the monovalent
vaccines. A recently conducted meta-analysis of published data for recombinant hepatitis B vaccines showed rates of approximately 95% for healthy adults.33 Recently, a study was performed with a competitor combined hepatitis A and B vaccine, showing a lower immune response to the hepatitis B antigen in the vaccine. The hepatitis B portion of the vaccine did not produce clinically acceptable seropositivity rates 4 weeks after the second injection (82.4%). This lack of antibody production was attributed, at least in part, to immunologic interference of the vaccine components.34
Also, the nature and incidence of local and general symptoms are similar to those reported for this vaccine. Very few of these symptoms were scored as severe. Type, incidence and severity of these symptoms following administration of the combined vaccine were also similar to those observed in clinical trials with the corresponding monovalent vaccines (Havrix and Engerix-B, Glaxo SmithKline).1-2 Only one serious adverse event was reported, and this was unlikely to be related to vaccination.
In conclusion, we have shown high immunogenicity and tolerance of the combined hepatitis A and B vaccine (Twinrix) in healthy Chilean adults. Combined vaccination against both hepatitis A and B has the advantage of offering dual protection, with a reduction in the number of injections needed, lower associated administration costs, and a positive impact on compliance.
ACKNOWLEDGMENTS
The authors wish to thank the participants in this clinical study and Dr Norbert De Clercq for his editorial assistance.
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