Do we need 3 doses of hepatitis B vaccine?

A model for establishment, maintenance and reactivation of the immune response after vaccination against Ebola virus

The 2014-2016 Ebola outbreak in West Africa has triggered accelerated development of several preventive vaccines against Ebola virus. Under the EBOVAC1 consortium, three phase I studies were carried out to assess safety and immunogenicity of a two-dose heterologous vaccination regimen developed by Janssen Vaccines and Prevention in collaboration with Bavarian Nordic. To describe the immune response induced by the two-dose heterologous vaccine regimen, we propose a mechanistic ODE based model, which takes into account the role of immunological memory. We perform identifiability and sensitivity analysis of the proposed model to establish which kind of biological data are ideally needed in order to accurately estimate parameters, and additionally, which of those are non-identifiable based on the available data. Antibody concentrations data from phase I studies have been used to calibrate the model and show its ability in reproducing the observed antibody dynamics. Together with other factors, the establishment of an effective and reactive immunological memory is of pivotal importance for several prophylactic vaccines. We show that introducing a memory compartment in our calibrated model allows to evaluate the magnitude of the immune response induced by a booster dose and its long-term persistence afterwards.

Hepatitis B Vaccination in Patients with Liver Cirrhosis Evaluated for Liver Transplantation - A Simple Intervention Ensures High Adherence

BACKGROUND There is an unmet need to improve the HBV vaccination status in patients with chronic liver diseases. Primary care physicians and outpatient hepatologists often fail to vaccinate as recommended. Thus, new strategies to improve the HBV vaccination rate are required. MATERIAL AND METHODS This study was performed in a cohort of patients with chronic liver diseases evaluated for liver transplantation. Vaccination status was taken from the patients' vaccination cards. HBsAg-, anti-HBc-, and anti-HBs-negative individuals were vaccinated against HBV at hospital discharge, and subsequent outpatient completion of the standard vaccination protocol was recommended in detail in the discharge letter. At months 2 and 8, titer controls were performed, and completion of vaccination was evaluated. RESULTS We prospectively recruited 37 patients. At baseline, the vaccination rate against HBV was 24% (N=9/37), and 3/9 HBV vaccinated patients presented with an anti-HBs-titer >10 IU/L. Thus, N=34 were vaccinated with Engerix® or Twinrix®. We evaluated 26/34 patients at month 2 and 10/26 again at month 8. The second vaccine dose was obtained by 21/26 (80%) of the patients seen at month 2, and 9/10 (90%) seen at month 8 obtained the third vaccine dose by primary care physicians or ambulant hepatologists. Only 2 patients presented with an anti-HBs-titer >10 IU/L at month 8. CONCLUSIONS Initiation of HBV vaccination during hospitalization and detailed recommendations on subsequent vaccinations in the discharge letter improve previously inadequate vaccination rates in the outpatient setting. Similar measures should be implemented at earlier time points of chronic liver diseases to achieve higher immune response rates.

A double-dose hepatitis B vaccination schedule in travelers presenting for late consultation

BACKGROUND

Vaccination against hepatitis B virus (HBV) is recommended for all travelers visiting HBV-endemic countries. However, travelers often present with insufficient time for the standard HBV vaccine schedule (SVS). We examined seroprotection against HBV following an alternative two-visit vaccination schedule (TVS) with currently available vaccine products, and completion rates with this TVS.

METHODS

A retrospective cohort study was conducted in three travel clinics in British Columbia, Canada. Adults ≥20 years old traveling to an HBV-endemic country, and unable to complete the standard or rapid HBV vaccination schedule before departure, were offered a TVS that consisted of a double dose of HBV vaccine at day 0, followed by a single dose in 4 to 12 months. Immunity to HBV [anti-HBV surface antigen (HBs) ≥10 mIU/mL] was determined 1 to 6 months following the final dose of HBV vaccine. Logistic regression modeling was used to assess correlates of seroprotection. We also determined completion rate with this TVS at two clinics.

RESULTS

In total, 117 participants (age range, 21-81 years, median age 57) met the inclusion criteria. Of these, 97 (82.9%) were immune after the TVS. Immunity was demonstrated in 93.1% of patients <50 years old and 79.5% of patients ≥50 years old. Increasing age was associated with reduced odds of developing immunity to HBV using the TVS [adjusted odds ratio = 0.954, 95% confidence interval (CI): 0.904, 1.008]. The completion rate of the TVS was 32.6% over a 12-month period. Completion rates varied between clinics (23.5% vs 48.4%, p < 0.001), suggesting that clinic-specific follow-up policies were important.

CONCLUSION

Seroprotection with completion of this TVS was similar to or exceeded that published in the literature for the SVS by age. However, even with a TVS, completion rates were low, underscoring the importance of follow-up. Further research is needed to determine whether travelers are protected prior to completion of this TVS.

Preclinical evaluation of a two-dose vaccination schedule of recombinant Hansenula polymorpha hepatitis B vaccine in animals

AIMS

The current 3-dose regimen of hepatitis B vaccination for infants requiring over 6 mo period may pose the poor rate of compliance and later protection from hepatitis B virus (HBV) infection. This preclinical study is to investigate the feasibility of reducing the number of doses of hepatitis B (HB) vaccine.

RESULTS

Eight groups of guinea pigs immunized with two doses of HP-HB vaccines at either 0 and 4 weeks or 0 and 8 weeks elicited geometric titers (GMT) of anti-HBs similar to that of four groups immunized with three doses of controls. The overall GMT of anti-HBs were not significantly different between the E- and C-groups (p>0.05) of monkeys. Specifically, the anti-HBs titers in the C-group reached the peak of 24857 (938.3-104585) mIU/mL one week after the 3rd dose, which were statistically higher than those of the E-group. However, they were reduced to comparable levels of anti-HBs in the E-group during weeks 9-12, suggesting comparable immune response of both vaccination regimens.

METHODS

Twelve groups of guinea pigs (four animals in each group) were immunized with 2 experimental recombinant yeast Hansenula Polymorpha derived HB vaccines (HP-HB vaccine) and 2 commercial recombinant yeast Saccharomyces Cerevisiae vaccines (Temrevac-HB) as controls at 0, 4 and 8 weeks, 0 and 4 weeks, and 0 and 8 weeks respectively. Each guinea pig received 2 µg vaccine. Twelve Cynomolgus monkeys were randomly divided into two groups (six animals in each group). Animals in the experimental group (E-group) were injected with two doses of pilot produced 20 µg HP-HB vaccine. Animals in the control group (C-Group) were immunized with three doses of 10 µg Temrevac-HB. Both vaccines were administered at an interval of 3 weeks for monkeys.

CONCLUSIONS

The 2-dose regimen of the HP-HB vaccine has comparable HBV immune responses as the 3-dose regimen of Temrevac-HB vaccine in Cynomolgus monkeys.

Explaining observed infection and antibody age-profiles in populations with urogenital schistosomiasis

Urogenital schistosomiasis is a tropical disease infecting more than 100 million people in sub-Saharan Africa. Individuals in endemic areas endure repeated infections with long-lived schistosome worms, and also encounter larval and egg stages of the life cycle. Protective immunity against infection develops slowly with age. Distinctive age-related patterns of infection and specific antibody responses are seen in endemic areas, including an infection 'peak shift' and a switch in the antibody types produced. Deterministic models describing changing levels of infection and antibody with age in homogeneously exposed populations were developed to identify the key mechanisms underlying the antibody switch, and to test two theories for the slow development of protective immunity: that (i) exposure to dying (long-lived) worms, or (ii) experience of a threshold level of antigen, is necessary to stimulate protective antibody. Different model structures were explored, including alternative stages of the life cycle as the main antigenic source and the principal target of protective antibody, different worm survival distributions, antigen thresholds and immune cross-regulation. Models were identified which could reproduce patterns of infection and antibody consistent with field data. Models with dying worms as the main source of protective antigen could reproduce all of these patterns, but so could some models with other continually-encountered life stages acting as the principal antigen source. An antigen threshold enhanced the ability of the model to replicate these patterns, but was not essential for it to do so. Models including either non-exponential worm survival or cross-regulation were more likely to be able to reproduce field patterns, but neither of these was absolutely required. The combination of life cycle stage stimulating, and targeted by, antibody was found to be critical in determining whether models could successfully reproduce patterns in the data, and a number of combinations were excluded as being inconsistent with field data.

Twenty-two years follow-up of a prospective randomized trial of hepatitis B vaccines without booster dose in children: final report

Long-term immunogenicity and efficacy of HBVvaccination with different regimens of HBV vaccines (A: 2-dose recombinant vs. B: 3-dose recombinant vs. C: 3-dose plasma-derived vaccines) without booster dose were examined in 318 Chinese children. Geometric mean titer (GMTs) of anti-HBs of group A subjects was significantly lower than that of groups B and C subjects at years 1, 5, 10 and 15. At year 22, the proportion of subjects with anti-HBs > or = 10 mlU/mL for groups A, B and C were 35.3%, 76.5% and 52.4%, respectively (p < 0.05 between groups A and B) in 55 subjects. In the 22 years study period, none was found to be HBsAg positive, and 72 subjects had > or = 1 episodes of anamnestic response. In conclusion, the 3-dose regimens have a better long-term immunogenicity. In terms of protection against HBV infection, the 2-dose and 3-dose vaccines had equal efficacies.

Mathematical model of the antibody response to hepatitis B vaccines: Implications for reduced schedules

One of the cardinal features of the immune response is immune memory: the size of the secondary antibody response to vaccination reflects the amount of immune memory that has been generated in an individual by the priming dose. We construct a mathematical model of the generation of immune memory and antibody in response to hepatitis B vaccines. The model predictions are compared to post-vaccination antibody titres from eight adult vaccine trials. The model demonstrates significant differences between different vaccines in both the time taken to generate immune memory and the amount of memory generated. The model provides theoretical support for the hypothesis that a single vaccine dose can generate protective immune memory.

Similar long-term vaccine efficacy of two versus three doses of HBV vaccine in early life

WHO currently recommends three vaccinations against hepatitis B to provide optimal protection against infection and carriage. However, immunological theory and mathematical modelling suggest that similar protection could be induced with two doses, and trials among adolescents and adults have shown comparable rates for both primary seroprotection and geometric mean titres following vaccination. We determined vaccine efficacy among 60 children who only received two doses of hepatitis B vaccine as infants and among 463 children who had received three doses after 4-7 years of follow-up. Vaccine efficacy among the two-dose group was 86.3% against anti-HBc positivity (infection) and 92.3% against HBsAg positivity (carriage), which was similar to the vaccine efficacy found among the participants who had received three doses. To confirm this comparable vaccine efficacy a randomised controlled non-inferiority trial with long-term follow-up is needed.

Immunological response to two hepatitis B vaccines administered in two different schedules

OBJECTIVES

To evaluate the antibody response to a plasma derived hepatitis B vaccine containing pre-S and S antigens and a recombinant vaccine containing only S antigen and compare the two vaccines in 0, 1, 2 and 0, 1, 6, schedules

METHODS

One hundred fifty nine healthy infants were randomized to receive the vaccines in two different schedules. Anti HBs titers were estimated prior to the vaccination and then one-month following the second and third doses.

RESULTS

Both the vaccines produced a high rate of seroconversion and seroprotection. The antibody response was similar with both the vaccines and the 0, 1, 6, schedule induced a significantly higher antibody level than the 0, 1, 2, schedule.

CONCLUSION

0, 1, 6 schedule produces a higher antibody level than 0, 1, 2 schedule though both the schedules have good seroconversion and seroprotection rates with both the vaccines.

Immunogenicity of two paediatric doses of monovalent hepatitis B or combined hepatitis A and B vaccine in 8–10-year-old children

Hepatitis A and B vaccines are highly immunogenic in three-dose schedules. To obtain an equivalent result in children with two paediatric doses would be of significant benefit. The purpose of this study was to measure the immunogenicity of a two-dose schedule in children with two licensed recombinant HBsAg containing vaccines given at paediatric doses, one of them combined with hepatitis A. Seven-hundred and four healthy school children aged 8-10 years were recruited in an open label study to receive either Twinrix Pediatric (360 El.U HAV antigen; 10 microg HBsAg) or Recombivax (2.5 microg HBsAg) vaccine intramuscularly 6 months apart. The seroconversion (>/=1 mIU/ml for anti-HBs antibodies and >/=33 mIU/ml for anti-HAV antibodies), seroprotection (anti-HBs >/=10 mIU/ml) rates and the geometric mean titers (GMTs) were determined 4-8 weeks after the second dose. The anti-HBs seroconversion rate was 97.1% with Twinrix and 97.2% with Recombivax. The seroprotection rates were 96.5 and 94.4%, respectively (P = 0.17). The GMT was higher with Twinrix than with Recombivax (3248 mIU/ml versus 742 mIU/ml, P < 0.0001). All the children vaccinated with Twinrix seroconverted to HAV and the GMT was 5168 mIU/ml. The obtained results suggest that two paediatric doses of hepatitis vaccines are highly immunogenic in 8-10-year-old children. This schedule could facilitate a greater vaccine acceptance and the addition of hepatitis A vaccine to existing adolescent universal hepatitis B virus immunization programs.

Recombivax-HB: perspectives past, present and future

Hepatitis B disease has caused a heavy burden worldwide. The development of an immunogenic, efficacious and safe vaccine to combat this problem has already eased this burden to some extent. The incorporation of the vaccine into the infant and childhood immunization schedule has led to a decrease in the number of new hepatitis B cases reported each year, and there has been a significant decline in hepatocellular carcinoma in children. This implies that the future will see less hepatitis B disease as the infant and adolescent population that has been immunized ages, meaning that the disease burden should fall even further.

The effect of late doses on the achievement of seroprotection and antibody titer levels with hepatitis b immunization among adolescents

OBJECTIVE

To determine the effect of varying dosing schedules and predictor variables on the seroprotection rates and geometric mean titer levels resulting from the hepatitis B vaccination series among adolescents.

METHODS

Adolescents received the hepatitis B vaccination series at varying schedules according to their natural adherence patterns. Data collected included participants' medication use; chronic illness; use of cigarettes, alcohol, and marijuana; age; race/ethnicity; and body mass index. Participants' dates of vaccinations were recorded and titer levels for hepatitis B surface antibody were drawn ~12 and 24 months after study enrollment. The data for 498 participants were analyzed using chi(2) tests, Student t tests, logistic regression models, and analysis of variance.

RESULTS

Seroprotection rates among adolescents were not affected by late vaccinations. The only factors affecting the achievement of seroprotection ~12 and 24 months after the first vaccination were body mass index and the number of immunizations received. Increased time between doses 1 and 2 and doses 2 and 3 showed a trend toward correlating with increasing titer levels.

CONCLUSIONS

Although adolescents at risk of acquiring hepatitis B should receive the hepatitis B vaccination series in a timely fashion, late doses are not detrimental, and may be beneficial, to achieving high antibody levels against the hepatitis B virus.

Double-dose accelerated hepatitis B vaccine in patients with end-stage liver disease

The aims of this study are to assess the efficacy of hepatitis B virus (HBV) vaccination using an accelerated schedule and double dose of recombinant vaccine in liver transplant recipients and identify factors associated with seroconversion and persistence of antibody to hepatitis B surface antigen (anti-HBs). Three hundred fifty-six patients were enrolled. Exclusion criteria were previous HBV infection, fulminant liver failure, or less than 2 years of follow-up after orthotopic liver transplantation (OLT). The vaccination schedule was 0, 2 weeks, 4 weeks, and 6 months using double-dose recombinant vaccine. Seroconversion was evaluated prospectively by measuring anti-HBs on the day of OLT and 1 and 2 years after OLT. Quantitative analyses of anti-HBs were performed retrospectively on stored sera. Geometric mean concentrations (GMCs) were calculated using a standard formula. All patients completed the full vaccination schedule, and 129 patients (36%) completed the schedule before OLT. The overall prevalence of anti-HBs was 128 of 356 pre-OLT samples (36%) compared with 41 of 353 (11.6%) and 26 of 325 post-OLT samples (8%) 1 and 2 years after OLT, respectively (both P =.001). The pre-OLT GMC was 86.7 compared with 0.32 and 0.33 at 1 and 2 years after OLT, respectively (P =.001). Patients with high titers of anti-HBs before OLT were more likely to have persistence of antibodies 1 or 2 years after OLT. Younger age (P =.02), low Child-Pugh score (P =.02), underlying chronic hepatitis C (P=.03), and specific host HLA subtypes were most strongly associated with seroconversion and/or persistence of anti-HBs. Thus, (1) seroconversion before or after OLT using double-dose accelerated-schedule vaccination against HBV is low, (2) there is a rapid, significant decrease in antibody titer after OLT, (3) pre-OLT anti-HBs titer potentially may be useful in predicting persistence of protective antibodies after OLT, and (4) several factors (age, genetic predisposition, severity of liver disease, and underlying liver disease) may have a role in poor vaccine responsiveness.