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Protection against hepatitis B disease relies on either protective serum antibodies or on the ability of the immune system to mount an anamnestic response when confronted with the hepatitis B virus (HBV). This open multicenter study (EUDRACT: 2010-022538-10) measured antibodies to HBV surface antigen (anti-HBs) in 7–8-year-old children who had received 4 doses of hexavalent diphtheria-tetanus-acellular pertussis-HBV-inactivated poliovirus-Hemophilus influenzae type b conjugate vaccine (DTPa-HBV-IPV/Hib: Infanrix™ hexa; GlaxoSmithKline Vaccines) in the first 2 years of life through routine vaccine services in Germany. The ability of these children to mount an anamnestic response to a challenge dose of monovalent HBV vaccine (Engerix™ B Kinder; GlaxoSmithKline Vaccines) was also assessed.
Before the challenge dose, 78.5% of children had anti-HBs levels ≥6.2 mIU/mL (seropositive) and 72.2% had anti-HBs levels ≥10 mIU/mL (seroprotected). Post-challenge, 98.9% had anti-HBs levels ≥10 mIU/mL and 95.8% had anti-HBs ≥100 mIU/mL. An anamnestic response to the challenge was observed in 96.6% of all subjects. The challenge dose was well tolerated, with a reactogenicity and safety profile consistent with published data. DTPa-HBV-IPV/Hib induces long-lasting immune memory to HBV that appears very similar to that induced by monovalent HBV vaccines. Protection against hepatitis B may be conferred through immune memory in subjects who responded to primary vaccination, even when they subsequently lose detectable levels of circulating anti-HBs antibodies.
Protection against hepatitis B disease relies on either circulating protective serum antibodies or on the ability of the immune system to mount an anamnestic response when confronted with the hepatitis B virus (HBV). Studies conducted after primary vaccination of infants with monovalent recombinant HBV vaccines show persisting immune memory responses up to 20 y after vaccination.1,2 Based on such data, consensus groups, including the World Health Organization (WHO), the European Union Consensus Group and the Viral Hepatitis Prevention Board do not recommend administration of booster doses after primary vaccination in immunologically competent individuals.3,4,5
The HBV antigen may be administered as a monovalent vaccine, such as Engerix™ B (GlaxoSmithKline Vaccines), or in multivalent combination vaccines that facilitate inclusion and uptake in infant vaccination schedules. The combined hexavalent diphtheria-tetanus-pertussis-HBV-inactivated poliomyelitis and Hemophilus influenzae type b conjugate vaccine (DTPa-HBV-IPV/Hib, Infanrix™ hexa; GlaxoSmithKline Vaccines) has been licensed for the primary vaccination of infants and as a booster dose in the second year of life since 2000. The immunogenicity and tolerability of DTPa-HBV-IPV/Hib has been extensively documented in clinical trials, and through 12 y of post-marketing experience.6,7 Combining the hepatitis B surface antigen (HBsAg) with other vaccines routinely administered in infancy promotes higher coverage than can be achieved using monovalent vaccines, or through vaccination programmes targeting adolescents and at-risk groups.8,9,10 HBV vaccination is important even in countries of low endemicity, where a proportion of chronic disease cases arise through perinatal or early childhood infections.11
Many of the long-term follow up studies of HBV immunity have been performed in cohorts vaccinated in infancy with monovalent HBV vaccines. However, it is important to establish that protection against hepatitis B after vaccination with combination vaccines will also be long lasting.
In Germany, the routine infant vaccination schedule, including the HBV vaccine, is given at 2, 3, and 4 mo of age and a booster dose is given before 18 mo of age. Here we report antibody persistence in healthy 7–8 y old children who received 4 doses of DTPa-HBV-IPV/Hib in the first 2 years of life through routine vaccine services in Germany. The ability of the children to mount an anamnestic response to a challenge dose of HBV was also assessed.
This study is the second of a series of 4 studies evaluating anti-HBs persistence and immune memory after infant vaccination with DTPa-HBV-IPV/Hib in routine clinical practice. The studies will evaluate progressively older cohorts in Germany, as they become available. Evaluation of the 5-y-old cohort study was reported previously.12
Of the 300 subjects who were enrolled and vaccinated in this phase IV, open-label study, 3 were eliminated from all of the statistical analyses—one subject was found to have received primary vaccination with a vaccine other than Infanrix™ hexa, one subject had missing laboratory results, and one subject provided duplicate blood samples after the challenge dose. Thirteen subjects were eliminated from the according-to-protocol (ATP) immunogenicity analysis because they violated protocol-specified inclusion or exclusion criteria (n = 10)—had not complied with the blood sampling schedule (n = 2) or had missing serological data (n = 1). The ATP immunogenicity cohort consisted of 284 subjects with a mean age of 7.5 y (standard deviation [SD] 0.5), of which 48.9% (139) were female. All but 2 subjects (99.3%) were Caucasian.
In this study 78.5% (223/284) of 7–8 y olds had persisting antibodies to HBV surface antigen (anti-HBs) levels ≥6.2 mIU/mL (seropositive) and 72.2% (205/284) had anti-HBs levels ≥10 mIU/mL (seroprotected). One month after the challenge dose, 98.9% (259/262) of children had anti-HBs ≥10 mIU/mL and 95.8% (251/262) had anti-HBs levels ≥100 mIU/mL (Table 1).
An anamnestic response to the HBV vaccine challenge (defined as a 4-fold or greater increase in the post-challenge anti-HBs antibody concentration in subjects who were seropositive prior to the challenge dose—or a post-challenge anti-HBs antibody concentration ≥10 mIU/mL in initially seronegative subjects) was observed in 96.6% (253/262) of subjects overall (Table 2). The anti-HBs antibody geometric mean antibody concentration (GMC) increased by 132-fold compared with pre-challenge concentrations.
Sixty-one children had undetectable pre-challenge anti-HBs antibodies (<6.2 mIU/mL; i.e., seronegative, Table 1). Of the 58 who had post-challenge results, 55 (94.8%) reached the 10 mIU/mL cut off after the challenge dose (an anamnestic response). Eighteen children had anti-HBs 6.2- <10 mIU/mL) before the challenge dose. Of the 15 subjects with post-challenge results, all recorded anti-HBs concentrations ≥10 mIU/mL after the challenge dose.
About 50% of the variation in response variable (post-challenge dose results) is explained by the pre-challenge dose results (Fig. 1, R2 0.5093).
Within 4 d (Day 0–3) of vaccination with monovalent HBV, pain was reported by 30.6% (95% confidence interval [CI]: 25.4%; 36.2%) of subjects, redness by 28.3% (95% CI: 23.2%; 33.8%), and swelling by 16.5% (95% CI: 12.5%; 21.2%) of subjects. Fatigue, gastrointestinal symptoms, headache, and fever were reported by 12.5% (95% CI: 8.9%; 16.8%), 9.1% (95% CI: 6.1%; 13.0%), 12.1% (95% CI: 8.6%; 16.4%), and 4.7% (95% CI: 2.6%; 7.8%) of subjects, respectively. Solicited symptoms of grade 3 intensity were reported by 1.7% of subjects or fewer. One unsolicited adverse event (injection site hematoma) reported within 31 d after vaccination was considered by the investigator to be related to vaccination. Three serious adverse events reported in 2 children occurred during the study—one subject had an allergic reaction 15 d after vaccination, one subject experienced Lyme disease and facial palsy that began 39 d after vaccination. None of the serious adverse events were considered by the investigator to be vaccine related, and all resolved.
Primary and booster vaccination of infants with DTPa-HBV-IPV/Hib in routine practice induced sustained immune memory to HBV until 7–8 y of age. More than 70% of children retained anti-HBs antibody concentrations ≥10 mIU/mL at 7–8 y of age, i.e., more than 6 and a half years after their fourth dose of DTPa-HBV-IPV/Hib. The majority of subjects with undetectable anti-HBs antibody concentrations at the time of the challenge dose showed evidence of immune memory, with many-fold increases in anti-HBs antibody concentrations observed after the challenge dose. This is consistent with other studies undertaken in populations of low HBV endemicity where immune memory has been shown to persist in individuals primed with monovalent HBV or other recombinant vaccines in whom circulating antibody has been lost.13,14,15 We observed only a moderate correlation between pre- and post-challenge anti-HBs concentrations, implying that the magnitude of the post-challenge response was not directly associated with the level of persisting anti-HBs antibodies prior to challenge. Furthermore, an anamnestic response was demonstrated in a similar proportion of subjects regardless of their seroprotection status before the challenge (94.8% and 100% with pre-challenge anti-HBs concentrations <6.2 and 6.2- <10 mIU/mL, respectively compared with 96.8% in those with pre-challenge concentrations ≥10 mIU/mL). These observations bring additional evidence to the notion that immune memory to hepatitis B is not driven only by the presence of persisting antibodies, but by persisting memory cells capable of responding rapidly to antigen exposure16,17
This study builds on a growing body of evidence demonstrating prolonged persistence of immune memory to HBV after primary vaccination with DTPa-HBV-IPV/Hib (summarized for countries, like Germany with a low HBV endemicity in Table 3). In clinical trials in Germany, in which children were vaccinated with 4 doses of DTPa-HBV-IPV/Hib in infancy, between 85.3% and 91.0% had persisting anti-HBs ≥10 mIU/mL at 4–6 y of age.12,18,19 This compares with anti-HBs ≥10 mIU/mL in 92.9% of 4–6 y old vaccinated with 4 doses of Engerix™ B.18 An anamnestic response to the challenge dose was observed in 95.7% to 96.8% of DTPa-HBV-IPV/Hib-primed children.12,19 In 7- to 9-y-old children vaccinated with 4 doses of DTPa-HBV-IPV/Hib in infancy, anti-HBs concentrations ≥10 mIU/mL persisted in 78.0% of subjects and an anamnestic response was observed in 98.9%.19 These results are consistent with those of the present analysis.
Our results are also consistent with findings of a study in a similar population vaccinated with monovalent HBV vaccine.20 In 7- to 8-y-old German children vaccinated in infancy with 3 doses of monovalent HBV through routine vaccination services, 83.3% had persisting anti-HBs ≥10 mIU/mL. Of the 21/280 children with undetectable anti-HBs prior to the challenge dose, all demonstrated an anamnestic response to challenge.20 These studies indicate that the persistence of antibodies and immune memory is similar after vaccination with monovalent HBV or DTPa-HBV-IPV/Hib.
The challenge dose was well tolerated, with a reactogenicity and safety profile in line with published data on monovalent HBV.21
Although limited by the absence of a control group vaccinated with monovalent HBV vaccine, this study provides evidence of the long-term immunogenicity of DTPa-HBV-IPV/Hib in subjects vaccinated in a routine clinical practice setting.
DTPa-HBV-IPV/Hib induces long-lasting immune memory to HBV that appears to be very similar to that induced by monovalent HBV vaccines.18,20 Protection against HBV infection may be conferred through immune memory in subjects who responded to primary vaccination, even when they subsequently lose detectable levels of circulating anti-HBs antibodies.
This open study was conducted in 12 centers in Germany between 26 April 2011 and 28 September 2011 (EUDRACT: 2010-022538-10). The protocol was approved by the Landesärztekammer Baden-Württemberg Ethics committee. The study was conducted in accordance with Good Clinical Practice and the Declaration of Helsinki. Written informed consent was obtained from subject’s parent/legally acceptable representative prior to enrolment.
Participants were healthy with documented evidence of previous vaccination with 4 consecutive doses of Infanrix™ hexa as part of routine vaccination in Germany—3 doses of primary vaccination received by 9 mo of age and one booster dose received between 11 and 18 mo of age. Children who had received HBV vaccine at birth or any HBV vaccine after the fourth dose administered in the second year of life, and those with a history of HBV infection, were excluded. Children were also excluded if they were immunosuppressed from any cause, including chronic (>14 d) receipt of oral immunosuppressant medication.
All eligible subjects received a single challenge dose of monovalent HBV vaccine (Engerix™ B Kinder; GlaxoSmithKline Vaccines) administered intramuscularly into the deltoid region of the non-dominant arm.
A blood sample was taken before and one month after the challenge dose. Anti-HBs antibodies were measured using an FDA approved and EU marketed Chemiluminescence Immunoassay (CLIA) (Centaur™) with a cut-off of 6.2 mIU/mL defining seropositivity. Previous HBV infection, as evidenced by testing seropositive for antibodies against hepatitis B core antigen (anti-HBc), was determined in all children at the post-challenge blood sampling time-point. No samples were found to be anti-HBc positive.
Reactogenicity was assessed using diary cards that were provided to participants at the first study visit. Parents of children were asked to record any solicited local and general adverse events that occurred during 4-d (Day 0–3) follow-up after the challenge dose. The occurrence of solicited local (pain, redness, and swelling) and general (fatigue, gastrointestinal symptoms, headache, and fever) adverse events that occurred during 4-d (Day 0–3) follow-up after the challenge dose was recorded. Grade 3 (severe) symptoms were defined as redness or swelling ≥50 mm diameter—temperature >39.0 °C—and as preventing normal activity for all other symptoms. All other adverse events were recorded for 31 d after vaccination. Serious adverse events were recorded over the entire study period.
The primary objective of the study was to assess the percentage of subjects who achieved anti-HBs antibody concentrations ≥100 mIU/mL after the challenge dose. A sample size of 270 evaluable subjects provided 86% power for the lower limit of the 95% CI for the percentage of subjects with anti-HBs antibody concentrations ≥100 mIU/mL one month post- challenge to be >90%, if the true percentage of responders was 95%.
The Total Vaccinated Cohort included all subjects who received the HBV challenge dose. The ATP Immunogenicity Cohort included all eligible subjects who received the challenge dose, who met eligibility criteria, complied with protocol-defined procedures and who had post-challenge blood sampling results available.
G.B.: No potential conflicts of interest were disclosed. O.V.M. and P.C. are employees of GlaxoSmithKline Biologicals SA.
The authors thank the children and their parents who participated in the study and Dr Ulrich Behre, Dr Philipe Fellner von Feldegg, Dr Martin Kimmig, Dr Ralph Maier, Dr Lothar Maurer, Dr Michael Steiner, Dr Uta Wlather, and the other investigators who enrolled subjects at their centers. The authors also thank Petra Vandenberk and Britta Gartner (both GSK) for coordinating and managing the study, Joanne Wolter (independent medical writer, Australia, on behalf of GSK) for preparing the first draft of the manuscript, and Julia Donnelly (freelance publication manager, United Kingdom, on behalf of GSK) for editorial assistance. INFANRIX and ENGERIX are trademarks of the GlaxoSmithKline group of companies. Centaur is a trademark of Siemens, Germany.
GB was the principal investigator and together with OVM contributed to the conception, design, analysis, and interpretation of the study. PDC undertook the statistical analysis. All authors critically reviewed and approved this manuscript for submission.
This study was sponsored and funded by GlaxoSmithKline Biologicals S.A., Rixensart, Belgium. GlaxoSmithKline Biologicals S.A. was involved in all stages of the study conduct and analysis—and also took charge of all costs associated with the development and the publishing of the manuscript.