Haemophilus influenzae Type b Conjugate and Combination Vaccines

Immunological memory and nasopharyngeal carriage in 4-year-old children previously primed and boosted with 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) with or without concomitant prophylactic paracetamol

BACKGROUND

Prophylactic paracetamol (PP) was previously shown to reduce primary and booster antibody responses against the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV). This study further evaluated the effect of PP on antibody persistence, immunological memory and nasopharyngeal carriage (NPC).

METHODS

Two hundred and twenty children previously primed (3 doses, NCT00370318) and boosted (NCT00496015) with PHiD-CV with (PP group) or without (NPP group) prophylactic paracetamol administration received one PHiD-CV dose in their fourth year of life to assess the induction of immunological memory following previous immunisations. A control group of age-matched unprimed children enrolled in study NCT00496015 received an investigational tetravalent Neisseria meningitidis serogroups A, C, W-135, Y tetanus toxoid-conjugate vaccine, and thus remained unprimed for pneumococcal vaccination. Of these, 223 unprimed children received in the present study at least one PHiD-CV dose of a 2-dose catch-up regimen, which was relevant as control for assessment of immunological memory in PHiD-CV primed children.

RESULTS

Induction of immunological memory was shown irrespective of PP administration at primary and booster vaccination. Antibody geometric mean concentrations were lower in the PP group for serotypes 1, 4, 7F and 9V. Opsonophagocytic titres did not differ significantly between PP and NPP groups. Previous use of PP seemed to have only a minor impact on kinetics of antibody persistence. Reduced NPC of vaccine pneumococcal serotypes and trends towards increased NPC of non-vaccine and non-cross-reactive serotypes were seen in primed groups versus the control group, with no obvious differences between PP and NPP groups.

CONCLUSION

Regardless of whether previous PHiD-CV vaccination was given with or without PP, induction of immunological memory and persistence of PHiD-CV's impact on carriage was seen until at least 28 months post-booster vaccination. Our study results therefore suggest that the lower immune responses after primary and booster vaccination with PP are of transient nature.

Anamnestic immune response in 3- to 4-year-old children previously immunized with 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine as 2-dose or 3-dose priming and a booster dose in the first year of life

BACKGROUND

Immunogenicity of 10-valent pneumococcal nontypeable Haemophilus influenzae protein d conjugate vaccine (PHiD-CV), administered as 2-dose or 3-dose priming followed by a booster dose, has been described previously. The present study evaluated immunologic memory following PHiD-CV vaccination according to these vaccination schedules.

METHODS

A dose of PHiD-CV (to test anamnestic responses) was administered to 172 children at 36 to 46 months of age; 110 of them had previously been vaccinated with PHiD-CV according to 2 + 1 or 3 + 1 schedules (PHiD-CV [2 + 1] and PHiD-CV [3 + 1] groups) and 62 were unprimed age-matched controls. To measure immune responses before and 7 to 10 days after the PHiD-CV dose, 22F-inhibition enzyme-linked immunosorbent assay and opsonophagocytic activity (OPA) assay were used.

RESULTS

Serotype-specific IgG geometric mean concentrations (GMCs) and OPA geometric mean titers increased substantially (from before to 7 to 10 days after the additional PHiD-CV dose) for all 10 vaccines and 2 cross-reactive serotypes (6A and 19A) in the children previously vaccinated with PHiD-CV, regardless of the vaccination schedule used. Antibody GMCs and OPA geometric mean titers after the administration of the PHiD-CV dose were markedly higher in both previously PHiD-CV-vaccinated groups than in the unprimed control group, clearly demonstrating prior induction of immunologic memory. Antiprotein D antibody GMCs had also increased substantially from before to 7 to 10 days after vaccination in all 3 groups, with higher antibody GMCs in the previously vaccinated groups than in the control group.

CONCLUSION

PHiD-CV vaccination according to 2 + 1 or 3 + 1 schedules resulted in comparable anamnestic immune responses. These findings suggest that similar protective efficacy may be achieved with both the schedules.

Quality of the Haemophilus influenzae type b (Hib) antibody response induced by diphtheria-tetanus-acellular pertussis/Hib combination vaccines

It has been repeatedly observed that mixing Haemophilus influenzae type b (Hib) conjugate vaccines with acellular pertussis-containing vaccines (diphtheria-tetanus-acellular pertussis [DTPa]) resulted in a reduced magnitude of the anti-polyriboseribitolphosphate antibody response compared to that obtained when Hib vaccines were administered separately and not mixed. Nevertheless, the quality and functionality of the immune responses have been shown to be the same. With the purpose of investigating the quality of the anti-Hib immune responses that are elicited under different vaccination regimens, we report here four primary and booster-based pediatric clinical trials in which Hib vaccine was either mixed with DTPa or diphtheria-tetanus-whole-cell pertussis (DTPw)-based vaccines or was coadministered. Our results show that avidity maturation of the antibodies was lower when primary vaccination involved DTPa mixed with Hib compared to when DTPa and Hib were coadministered. No such difference was observed between mixed and separately administered Hib when associated with DTPa-hepatitis B virus-inactivated poliovirus or DTPw-based vaccines. All different combinations and regimens elicited the same opsonophagocytic and bactericidal activity as well as the same ability to protect in a passive infant rat protection assay. The functional activity of mixed DTPa-based and Hib vaccines was similar to that of mixed DTPw-based/Hib combinations. In conclusion, in vitro and in vivo data as well as postmarketing vaccine effectiveness data attest to the ability of DTPa-based/Hib combination vaccines to effectively prevent Hib-induced disease in children.

Reactogenicity and immunogenicity profiles of a novel pentavalent diphtheria-tetanus-whole cell pertussis-hepatitis B and Haemophilus influenzae type B vaccine: a randomized dose-ranging trial of the Hib tetanus-conjugate content

BACKGROUND

Combined vaccines containing diphtheria-tetanus-pertussis whole-cell (DTPw), Haemophilus influenzae type b (Hib), and hepatitis-B vaccines are essential for the continuing success of vaccination programs in developing nations. This randomized, dose-ranging study assessed the immunogenicity and reactogenicity of primary and booster vaccination with pentavalent DTPw-HBV/Hib vaccines containing 10, 5 or 2.5 microg of polyribosylribitol phosphate (PRP) conjugated to tetanus toxoid (trials Hib-052/064).

METHODS

Six hundred eighty infants were randomized to receive one of 5 vaccine combinations at 6, 10, and 14 weeks of age. Of these, 351 received the same vaccine at 15-24 months of age. The immune response was evaluated on blood samples collected 1 month after the 3-dose primary course and before and 6 weeks after the booster dose. Reactogenicity was assessed during a 4-day period after each vaccine dose using diary cards.

RESULTS

After primary vaccination, all subjects had seroprotective anti-PRP antibody concentrations (> or = 0.15 microg/mL) and > 95% had concentrations > or = 1.0 microg/mL, irrespective of the PRP dose administered. Anti-PRP antibody avidity after primary vaccination and antibody persistence until the second year of life were similar among groups. The booster dose induced marked increases in anti-PRP antibody GMCs and antibody avidity, indicative of effective priming and the presence of immune memory. All vaccination regimens elicited good immune responses and comparable antibody persistence to the other vaccine antigens, with significant increases in all antibody concentrations observed after boosting. All vaccination regimens were safe, with similar overall reactogenicity profiles.

CONCLUSION

Hib conjugate vaccines containing reduced amounts of PRP can be effectively combined with the licensed DTPw-HBV vaccine to provide protection against 5 major childhood pathogens in a single injection.

Avidity determinations for Haemophilus influenzae Type b anti-polyribosylribitol phosphate antibodies

Determination of antibody avidity measurements can be difficult in human serum depending on the population evaluated. We evaluated three approaches for the determination of antibody avidity for immunoglobulin G (IgG). These approaches were (i) elution of bound antibody with increasing concentrations of a chaotropic agent using a single serum dilution, (ii) binding interference of multiple serum dilutions by a single concentration of a chaotrope, and (iii) elution of multiple serum dilutions by a single concentration of a chaotrope. Parameters that affect the determination of avidity measurements and their limitations were evaluated with pre- and post-Haemophilus influenzae type b conjugate vaccination sera (n=89). We determined that elution of low-avidity antibodies present in multiple dilutions of the serum sample by a single concentration of a chaotrope (0.15 M sodium thiocyanate [NaSCN]) was optimal for the determination of avidity measurements throughout a wide range of IgG concentrations (0.94 to 304.6 microg/ml). The percent reduction in concentration as determined by the elution assay with 0.15 M NaSCN correlated highly (r=0.84) with weighted averages obtained by an elution assay with multiple solutions of NaSCN. The correlation (r=0.57) between elution and binding interference, when a single concentration of a chaotrope was used, was lower than the correlation between the two elution methods (r=0.84). We found that the serum dilution, the heterogeneity of the antibody population, and the concentration of the chaotrope were the primary variables affecting avidity determinations. In this study, we present multiple analysis methods depending on the methodology used. We also present the factors that affect the analysis of avidity determinations given the polyclonal nature of human sera. This experimental approach should benefit the evaluation of similar antibodies induced by other bacterial polysaccharide vaccines.

Statistical considerations for vaccine immunogenicity trials. Part 1: Introduction and bioassay design and analysis

The foundation for any vaccine immunogenicity trial is the identification of appropriate correlates for protection and the measurement of these quantities with well-designed bioassays. An important requirement for developing bioassay protocols is the standardization of each procedure, so it is performed in a uniform manner within a facility and, in the case of multicenter trials, across laboratories. It is also crucial to recognize that the selection and use of techniques used to quantify assay endpoints (e.g., antibody concentration) will affect their accuracy and precision and these methods must also be defined and uniformly applied within and across laboratories. This paper discusses a number of methodological issues related to bioassay design and analysis that would ultimately lead to highly accurate assay endpoint determinations with minimum variance that would be comparable across laboratories. Guidelines are presented for the development of bioassay and data analysis protocols. Strengthening vaccine immunogenicity trial protocols will ensure that these quantities are estimated with the greatest degree of reliability and facilitate the subsequent evaluation of new vaccine formulations. Following these guidelines will give other researchers as well as regulatory authorities more confidence in evaluating and comparing the differences in immunogenicity levels elicited by new and developing vaccines.

Bridging phase 2 and phase 3 pneumococcal immunologic data for future combination vaccines

Pneumococcal conjugate vaccines (PncCs) will be introduced into childhood vaccination programs now that the first PncC has been licensed for use. The next generation of PncCs and possible combination vaccines containing PncC will most probably be approved on the basis of phase 2 immunogenicity and safety data. PncCs are combination vaccines that include, at present, 7-11 components. Immune response to different components may vary. Furthermore, there seem to be population-based differences in immune response. Whether these differences are due to the other vaccines that are given simultaneously or due to the genetic background remains to be seen. Immune response can be evaluated by determining both the quantity and the quality of antibodies after vaccination. However, data are still missing on the minimal protective immune response and serologic correlates or surrogates of protection.

Clinical relevance of lower Hib response in DTPa-based combination vaccines

Combination vaccines are essential to enable administration of all the required antigens in routine infant immunisation schedules at any single visit. Some combinations of diphtheria-tetanus-acellular pertussis (DTPa) with Haemophilus influenzae type b (Hib) conjugate vaccines have been shown to result in lower Hib titres than when Hib is administered separately. While confirming that a primary series with a DTPa-HBV-IPV/Hib combination gives lower antibody levels than separate Hib conjugates, we show that the nature (isotype and IgG subclasses) and function (avidity and opsonic activity) of the antibodies are the same, and immunologic memory is induced. It is likely therefore that the DTPa-HBV-IPV/Hib combination will be efficacious against Hib disease.

A new DTPa-HBV-IPV vaccine co-administered with Hib, compared to a commercially available DTPw-IPV/Hib vaccine co-administered with HBV, given at 6, 10 and 14 weeks following HBV at birth

Three hundred and twenty eligible infants were enrolled in an open randomized clinical trial and allocated to one of two groups to receive either separate concomitant injections of a candidate combined DTPa-HBV-IPV and commercial Hib vaccine (candidate administration: DTPa-HBV-IPV+Hib) or separate concomitant injections of licensed DTPw-IPV mixed in the same syringe with Hib and HBV vaccines (comparator administration: DTPw-IPV/Hib+HBV). Vaccines were administered at 6, 10 and 14 weeks of age preceded by a monovalent dose of HBV at birth. The candidate vaccine administration was shown to be at least as immunogenic (primary objective) as the candidate administration with respect to the diphtheria, tetanus, polio, HBs and PRP seroprotection rates (primary endpoints). Post vaccination, both vaccine administrations showed an equivalent level of seroprotection with nearly all subjects (>96%) acquiring seroprotective titers against diphtheria, tetanus, polioviruses, HBsAg and PRP antigens. A markedly higher anti-HBs response post dose 2 at week 14 in the group receiving the candidate vaccine, 98.6% of subjects had seroprotective titers (GMT of 505.7 mIU/ml) compared with only 88.7% (GMT of 107.5 mIU/ml) in the comparator group. There was a lower incidence of adverse events following the DTPa-based candidate administration compared with the DTPw-based comparator. Despite the early age and short interval between doses, both administrations were immunogenic, with the concomitant administration of DTPa-HBV-IPV and Hib vaccines showing an improved tolerability over the commercial vaccines DTPw-IPV/Hib and HBV.

Primary vaccination of infants with diphtheria-tetanus-acellular pertussis-hepatitis B virus- inactivated polio virus and Haemophilus influenzae type b vaccines given as either separate or mixed injections

OBJECTIVE

The aim of this open, multicenter, randomized trial was to evaluate the immunogenicity and reactogenicity of a candidate combined diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated polio virus (DTaP-HBV-IPV) vaccine when given as either a mixed or as separate concomitant injections with Haemophilus influenzae type b (Hib) vaccine.

STUDY DESIGN

A total of 359 subjects were randomized to receive either DTaP-HBV-IPV/Hib (mixed administration - 180 subjects) or DTaP-HBV-IPV + Hib (separate administration in opposite limbs - 179 subjects) at 2, 3, and 4 months of age.

RESULTS

After vaccination, seroprotective antibody concentrations against diphtheria, tetanus, hepatitis B, and polio viruses and a high (> or = 97%) pertussis vaccine response were seen in almost all study participants. All subjects except one in the mixed administration group had postvaccination Hib anti-PRP antibody concentrations > or = 0.15 microg/mL. Of subjects in the mixed and separate group, 77.2% (geometric mean antibody concentration, 2. 62 microg/mL) and 88.6% (geometric mean antibody concentration, 4.45 microg/mL) had Hib anti-PRP concentrations > or = 1 microg/mL, respectively. The addition of the Hib component to the 5-component vaccine did not increase the incidence of local or general reactions.

CONCLUSION

Both administrations of the candidate vaccine were found to be safe, immunogenic, and well tolerated. Although anti-PRP geometric mean antibody concentrations and the percent of subjects achieving the 1 microg/mL seroprotective level were lower after the mixed administration, they were in the range seen with monovalent Hib vaccines or with other DTaP-based/Hib combinations licensed in some European countries. Therefore both administrations have the potential to simplify childhood immunization.

Immunogenicity of pneumococcal conjugate vaccines

BACKGROUND

Prevention of pneumococcal infections is a public health priority because of the high impact of the disease and because of the increasing problems due to antimicrobial resistance. Traditional vaccines, consisting of purified capsular polysaccharides (PSs) of Streptococcus pneumoniae, are not immunogenic in young children. In addition they confer only limited protection in patients with immunodeficiencies and hematologic malignancies.

IMMUNOGENICITY OF PNEUMOCOCCAL CONJUGATE VACCINES

Immunogenicity of the PS vaccine has been enhanced by coupling pneumococcal PSs to proteins to produce a conjugate vaccine. Conjugate molecules are designed to possess T cell dependent properties, such as immunogenicity in early infancy, stimulation of high levels of IgG isotype antibodies and enhanced immunologic memory responses. In the clinical studies multivalent pneumococcal conjugate vaccines have been shown to induce an IgG-dominating serum antibody response against common pneumococcal serotypes causing infections in children. A booster dose later in life creates a robust and rapid antibody response, indicating the existence of immunologic memory in primed children. Antibodies induced by conjugate vaccines are functionally active, as demonstrated by their high avidity and opsonophagocytic activity.

Combined vaccination of Haemophilus influenzae type b conjugate and diphtheria-tetanus-pertussis containing acellular pertussis

After the introduction of effective Haemophilus influenzae type b (Hib) conjugate vaccines, clinical practice has driven the development of combination vaccines comprising Hib conjugates with the infant diphtheria-tetanus-pertussis (DTP) vaccines. However, when such combinations contain an acellular pertussis component (Pa), the antibody response to Hib is lower than that with separate injections and doubts have been raised about their efficacy. We believe that such concerns are unwarranted, since the serological correlates of efficacy previously applied for Hib polysaccharide vaccines seem inappropriate for Hib conjugates. Furthermore, our own studies have shown that the lower antibody responses are not associated with impaired function of the antibodies induced, nor, and possibly more importantly, with the induction of immune memory against Hib. Therefore, with the proviso that careful clinical surveillance of Hib disease is maintained, we encourage the introduction of DTPa-Hib combinations to facilitate the inclusion of Hib into the already crowded childhood immunisation schedule.