anti-Hib Antibody Research Articles

Haemophilus influenzae serotype b seroprevalence in central Lao PDR before and after vaccine introduction.

IntroductionVaccination has dramatically reduced invasive Haemophilus influenzae type b (Hib) disease worldwide. Hib vaccination was introduced in the Lao PDR in 2009, as part of the pentavalent vaccine. To contribute to the understanding of the epidemiology of Hib in Lao PDR and the protection levels before and after the introduction of the vaccination, we tested serum samples from existing cohorts of vaccine age-eligible children and unvaccinated adolescents for antibodies against Hib.MethodsSerum samples from 296 adolescents born before vaccine introduction and from 1017 children under 5 years (vaccinated and unvaccinated) were tested for anti-Hib antibodies by ELISA. Bivariate analyses were performed to investigate factors associated with long-term protection.ResultsThe vast majority of all participants showed evidence of short- (42.7%) or long-term (56.1%) protection against Hib. Almost all of the unvaccinated adolescents had antibody titers indicating short-term protection and almost half (45.6%) were long-term protected. Nearly all children (>99.0%) were at least short-term protected, even those that were unvaccinated or whose vaccination status was unknown. Among vaccinated children, participants vaccinated more than 1 or 2 years ago and with a mid-upper arm circumference z-score < -2 were less likely to be long-term protected.DiscussionNearly all adolescents born before the introduction of Hib vaccination in the Lao PDR had antibody titers corresponding to at least short-term protection, indicating a high burden of Hib disease at that time. After vaccine introduction, all but four children (>99%) showed at least short-term protection. Possible explanations for the proportion of protected, yet apparently unvaccinated children, may be past infections, cross-reacting antibodies or faulty vaccination documentation. Our results highlight the need for robust surveillance and reporting of invasive Hib disease to determine the burden of disease despite vaccination.

Lagging Immune Response to Haemophilus influenzae Serotype b (Hib) Conjugate Vaccine after the Primary Vaccination with Hib of Infants in The Netherlands.

In 1993, a Haemophilus influenzae serotype b (Hib) conjugate vaccine was introduced in the Dutch national immunization program, resulting in a sharp decrease in invasive Hib disease. We used a population-based set of serum samples collected in The Netherlands in 2006–2007 (Pienter-II, 5696 sera) to assess the concentration of antibodies to the capsular polysaccharide of Hib, and compared the results with those obtained from a similar set collected in 1995–1996 (Pienter-I, 7837 sera). Post-primary vaccination serum samples from children aged 6–11 months from the Pienter-II study contained approximately 4-fold lower anti-Hib antibody concentrations than samples from children from the Pienter-I study. No such difference was found in post-booster samples from children older than 11 months of age. In Pienter-II, the proportion of children aged 6–11 months with anti-Hib antibody concentrations below the putative protective concentration of 0.15 µg/mL was 30%, which is significantly higher than in the Pienter-I study (12%). Fewer children in the Pienter-II group developed antibodies able to kill Hib in a serum bactericidal assay compared to the Pienter-I children. The cause of the lagged response in Pienter-II children remain uncertain, but lack of natural boosting, interference by the acellular pertussis vaccine, combining vaccines and acceleration of the schedule may have contributed.

Antibodies prevalence against Haemophilus influenzae type b in Jeddah population, Saudi Arabia. II. Antibodies subclasses.

Our previous reported that Jeddah, Saudi Arabia population have a comparable and protective herd immunity represented by IgG, IgA and IgM against Haemophilus influenzae type b (Hib), by using indirect ELISA test was used to evaluate Haemophilus influenzae type b (Hib) anti-polyribosyl-ribitol phosphate (PRP) total antibodies (IgM, IgG, IgA) in 1,003sera samples. Current report was evaluated the IgG and IgA subclasses responsible about this protection using same methodology. IgG, IgA, and their subclasses are responsible about this circulating protection. Our study will consider the first report evaluate the levels of IgA subclasses and its relation to ages, as well as the relations between anti-Hib antibody subclass and age. The current results demonstrated that the highest levels concentrated in IgG1 and IgG2, while IgG3 and IgG4 showed the lowest levels. So, their concentrations were arranged in IgG1 > IgG2 > IgG3 > IgG4. The results indicated that the age and gender have no effect on both IgG or IgA subclasses in healthy immunized individuals enrolled. While, IgA1 concentrations were significantly higher than IgA2 in all age categories regardless of gender. It seem that the IgG1, IgG2 and IgA1 subclasses were the main constituent of Jeddah herd immunity against Hib. Finally, to the best of our knowledge, there were no previous reports that focusing on the levels of IgA subclasses and its relation to ages, so our study considers the first worldwide.

IgE anti-Haemophilus influenzae type b (Hib) antibodies detected in serum of Hib-vaccinated asthmatic and non-asthmatic pediatric patients.

Haemophilus influenzae type b (Hib) bacterium causes severe illness in infants and children, but has largely been eliminated by introducing a universal Hib conjugate vaccine. While effects of certain vaccinations on atopic disease have been studied, little is known about the relationship between Hib vaccination and diseases of altered immunoglobulin E (IgE) regulation (asthma or atopy). As such, it is necessary to provide more evidence concerning Hib vaccination as a possible risk factor for atopic disease. Total serum IgE and IgE-and IgG-anti-Hib antibody responses were studied in Hib vaccinated asthmatic (N.=14) and non-asthmatic children (N=26) (VaccZyme™ Human Anti Hib Enzyme Immunoassay Kit). Data are reported as mean optical density (OD) values. We found that: 1) total serum IgE levels were higher in asthmatic compared with non-asthmatic subjects (389±125 vs. 125±129, P<0.001); 2) IgE and IgG anti-Hib antibody responses were similar in both asthmatic and non-asthmatic subjects (0.722±0.279 and 0.681±0.280, respectively; P=0.65; 0.450±0.505 and 0.573±0.779, respectively; P=0.580). The universal Hib vaccine antigen did not result in either increased IgE, or IgG anti-Hib antibody responses in asthmatic or non-asthmatics subjects. Thus, in this cohort, no association between Hib vaccination and asthma status was identified.

Immunogenicity and safety of two doses of catch-up immunization with Haemophilus influenzae type b conjugate vaccine in Indian children living with HIV

BackgroundChildren living with HIV are at increased risk of disease from Haemophilus influenzae type b (Hib). Data are limited on the immunogenicity of a two-dose, catch-up schedule for Hib conjugate vaccine (HibCV) among HIV-infected children accessing antiretroviral therapy (ART) late. ObjectivesThe objectives of the study were to: (1) evaluate baseline immunity to Hib and the immunogenicity and safety of two doses of HibCV among HIV-infected Indian children; and (2) document the threshold antibody level required to prevent Hib colonization among HIV-infected children following immunization. MethodsWe conducted a prospective cohort study among HIV-infected children 2–15 years of age and HIV-uninfected children 2–5 years of age. HIV-infected children received two doses of HibCV and uninfected children received one. Serum anti-Hib PRP IgG antibodies were measured at baseline and two months after immunization in the HIV-infected children. Nasopharyngeal (NP) swabs were collected at baseline and follow-up. Results125 HIV-infected and 44 uninfected children participated. 40% of HIV-infected children were receiving ART and 26% had a viral load >100,000 copies/mL. The geometric mean concentration of serum anti-Hib PRP antibody increased from 0.25μg/mL at baseline to 2.65μg/mL after two doses of HibCV, representing a 10.6-fold increase (p<0.0001). 76% percent of HIV-infected children mounted an immune response. Moderate or severe immune suppression, trimethoprim/sulfamethoxazole prophylaxis, and lower baseline antibody levels were associated with lower post-vaccine serum anti-Hib PRP IgG antibodies. A serum anti-Hib PRP IgG antibody level ≥3.3μg/mL was protective against Hib NP colonization. There were no differences in adverse events between HIV-infected and uninfected children. ConclusionIncluding a catch-up immunization schedule for older HIV infected children in countries introducing Hib vaccines is important. Older HIV-infected children with delayed access to ART and without suppressed viral loads mounted an adequate immune response following two doses of HibCV.

Evaluation of safety and efficacy as an adjuvant for the chitosan-based vaccine delivery vehicle ViscoGel in a single-blind randomised Phase I/IIa clinical trial

ViscoGel, a chitosan-based hydrogel, has earlier been shown to improve humoral and cell-mediated immune responses in mice. In this study, a Phase I/IIa clinical trial was conducted to primarily evaluate safety and secondarily to study the effects of ViscoGel in combination with a model vaccine, Act-HIB to Haemophilus influenzae type b, administered as a single intramuscular injection. Healthy volunteers of both sexes, ages 22–50 and not previously vaccinated to HIB, were recruited. The trial had two phases. In Phase A, three ascending dose levels of ViscoGel (25, 50 and 75mg) were evaluated for safety in 3×10 subjects. Phase B had a single-blind, randomised, parallel-group design evaluating safety and efficacy in five groups, 20 subjects/group, comparing vaccination with 0.2μg or 2μg Act-HIB alone or combined with ViscoGel (50mg) and one group receiving the standard Act-HIB dose (10μg). No safety or tolerability concerns were identified. Local, transient reactions at the injection site were the most common adverse events. These were more frequent in groups receiving Act-HIB+ViscoGel, while other AEs were recorded at similar frequency in Act-HIB and Act-HIB+ViscoGel groups. Efficacy was evaluated by measuring serum anti-HIB antibodies and cellular responses in peripheral blood mononuclear cells (PBMC). There was a large variation in baseline anti-HIB antibody titres and no adjuvant effect was observed on the anti-HIB antibody production in groups vaccinated with Act-HIB+ViscoGel. ELISpot analyses revealed increased interferon-γ (IFN-γ) responses to Act-HIB in PBMCs from subjects vaccinated with Act-HIB in combination with ViscoGel, compared to groups receiving Act-HIB alone. Moreover, ViscoGel counteracted an inhibitory effect of Act-HIB vaccination on the IFN-γ response to both the vaccine itself and an irrelevant influenza antigen. In summary, ViscoGel was found to be safe and well-tolerated, supporting further examination of ViscoGel as a new innovative vehicle for vaccine development.

Antibodies against Haemophilus influenzae type b in The Gambia: Investigating the extent of protection across age groups

Following a landmark clinical trial, the vaccine against Haemophilus influenzae type b (Hib) was introduced in The Gambia in 1997. Whilst the immunogenicity of this vaccine is well established subsequent to the doses administered under the EPI schedule, little data exists assessing longevity of protection, using serology. Such data are needed however to predict the susceptibility to Hib at the population level.To determine antibody persistence in 5–6 year old fully vaccinated Gambian children compared with older children, adolescents and young adults, 427 serum samples from healthy 5–37 year old participants were tested for Hib antibodies using VaccZyme Human Anti-Hib ELISA kits.86% of the children who had received 3 doses of Hib vaccine in infancy had Hib antibody concentrations ≥0.15mg/l at the age of 5–6 years. This proportion was 76% for adolescents who had also largely been vaccinated and 90% for adults who had never received Hib vaccine.Although most participants had anti-Hib antibody above concentrations putatively defined as protective, significantly fewer had concentrations thought to confer long-term protection. This suggests a population with insufficient or waning antibody that may be susceptible to breakthrough disease and transmission.

The effect of rituximab on vaccine responses in patients with immune thrombocytopenia

AbstractB-cell depletion may impair vaccine responses and increase infection risk in patients with immune thrombocytopenia (ITP). We investigated the effects of rituximab on antibody and cellular responses to Streptococcus pneumoniae polysaccharide and Haemophilus influenzae type b (Hib) vaccines in ITP patients. Of 60 patients in the main trial, 24 patients received both vaccines 6 months after rituximab (n = 17) or placebo (n = 7). Among 20 evaluable patients, 3 of 14 (21%) in the rituximab group and 4 of 6 (67%) in the placebo group achieved a fourfold increase in anti-pneumococcal antibodies (P = .12). For anti-Hib antibodies, 4 of 14 (29%) and 5 of 6 (83%), respectively, achieved a fourfold increase (P < .05). Fewer patients in the rituximab group demonstrated Hib killing (2 of 14 [14%], 5 of 6 [83%], P < .05). Three of 14 rituximab-treated patients failed to respond to vaccines by any criteria. After vaccinations, preplasma cell blasts and interferon-γ–secreting T cells were reduced in rituximab-treated patients. Antibody responses were impaired for at least 6 months after rituximab. Cellular immunity was reduced in parallel with depleted B-cell pools. These findings have implications for the timing of vaccinations and the mechanism of infection after rituximab in ITP patients.

Specific antibodies against vaccine-preventable infections: a mother–infant cohort study

ObjectivesTo determine maternal and neonatal specific antibody levels to selected vaccine-preventable infections (pertussis, Haemophilus influenzae type b (Hib), tetanus and pneumococcus).DesignProspective cohort study.SettingA UK secondary care maternity unit (March 2011–January...

Safety and immunogenicity in 3-5 months-old infants after primary and boosting immunization with Hib PRP-TT conjugate vaccine

Objectives To evaluate the safety and immunogenicity of Haemophilus influenzae type b capsular-tetanus toxoid(Hib-TT) conjugate vaccine.Methods In an open-controlled,randomized trial,the eligible and consented infants of 3 to 5 months-old received 3 doses of Hib-TT or a licensed Hib-TT conjugate vaccine(Anerbao) as the control vaccine to evaluate safety; The serum anti-Hib PRP IgG antibody mean geometric concentration (GMC) in both groups after primary and boosting vaccination were measured by ELISA.Results No apparent difference in the frequency of total adverse reactions observed between two groups (study vaccine 23.85％ vs.comparator 31.40％) (x2=0.5,P＞0.05).The mild and severe fever reaction of both vaccines was 3.67％ and 4.48％ respectively,with no significant difference.The local reactions including erythema,swelling and induration reported was 1.22％ in study vaccine group.After 3 injections,the serum anti-Hib PRP IgG antibody GMC was 6.6686 μg/ml in study group and 7.5346 μg/ml in control group,with no significant difference in both of the antibody GMC (x2 =0.147,P=0.702).After one dose boosting injection,the serum antibody GMC in study group increased from 2.6396 μg/ml of preboosting to 6.2044 μg/ml of post-boosting.Conclusion The Hib-TT conjugate vaccine is proved to be safe in 3-5 months-old infants.The primary immune schedule for 3-5 months-old infants of 3 injections 1 month apart with the Hib-TT conjugate vaccine could induce IgG antibody response against Hib PRP with the GMC of long-term protection concentration in serum.A boosting dose after primary vaccination elicited obviously immunological memory. Key words: Hib-TT conjugate vaccine; Safety; Immunogenicity; Anti-Hib PRP IgG; Mean geometric concentration

Immune Response to Haemophilus influenzae Type b Vaccination in Patients with Chronic Renal Failure

Adult chronic renal failure patients undergoing hemodialysis are at an increased risk of invasive Haemophilus influenzae type b (Hib) disease due to the lack of functionally active anti-Hib antibodies. The pediatric Hib polysaccharide-protein conjugate vaccine is highly immunogenic in these patients and can provide protection against invasive Hib infection for at least 1 year.

Natural Immunity to Hemophilus influenza Type b in Children, South of Iran: Need for Vaccination

Hemophilus influenza type b (Hib) infection has a high morbidity and mortality rate especially in children less than 5 years of age. The incidence of Hib disease in Iran is not known and Hib vaccine is not included in the National Immunization Program. The aim of the present study was to investigate the level of antibody to Hib of children five years or younger living in Jahrom, Iran. Three hundred eighty six children 5 years or younger were selected by random sampling method. A blood samples were taken from those children. Anti-Hib IgG antibody (anti-PRP) level was determined in the serum by using anti-Hemophilus influenza IgG EIA kit (IBL, Germany). An anti-PRP antibody levels of 0.15 microg mL(-1) and over were accepted as the natural immunity. The mean concentration of Hib antibody was 0.94 +/- 0.480 microg mL(-1). Natural immunity was determined in three hundred and twenty six (84.5%) of the children. The proportion of natural immunity was increased from 64.9% among children = 12 month old to 95.2% in children aged 49-60 month (p < 0.001). The exposure rate of children with Hib was higher than expected, even in children who were just a few months old. Present data revealed need to be introducing Hib conjugate vaccine in the National Immunization Programs.

Immune response of adults with secondary immunodeficiency to pediatric Haemophilus influenzae type b (Hib) vaccine

Results Almost 90% of controls, but only 43% of non-vaccinated CRF patients had protective anti-Hib antibody. Four week post-vaccination, all but one patient (97%) have developed protective antibody with a 14-fold increase (P<0.05); in 29 out of 32 (91%) the antibody exhibited bactericidal activity. In the majority of patients, protective antibody persisted 9 months post-vaccine. The vaccine response did not depend on the age, but was lower in CRF patients who had type 2 diabetes, COPD, or heart disease, compared to the rest of the group. Conclusion Most adult patients with CRF are at an increased risk of acquiring invasive Hib disease as they lack protective antibody. The pediatric Hib vaccine is highly immunogenic in this group, with higher response compared to other vaccines administered to such patients (hepatitis B and pneumococcal vaccines). This study provides rationale for the immunization of individuals with secondary immnunodeficiency against Hib to achieve protective immunity.

A Randomized, Multicenter, Open-Label Clinical Trial to Assess the Immunogenicity of a Meningococcal C Vaccine Booster Dose Administered to Children Aged 14 to 18 Months

A booster meningococcal C (MenC) vaccine dose is recommended after the first year of life. The objective of this study was to assess its immunogenicity and factors that modify the immunoresponse. An open label study in which 389 children 14 to 18 months of age, previously primed with 3 doses of a MenC vaccine conjugated with CRM197 (MenC-CRM) or with 2 doses of a MenC vaccine conjugated with tetanus toxoid (MenC-TT), were randomized to be boosted with either of these vaccines and a DTaP-IPV-Hib vaccine at the same time. Immunogenicity against MenC and Haemophilus influenzae type b was assessed before and 1 month after the booster dose. Before the second year booster, 44.9% of the studied children had MenC bactericidal (SBA) seroprotection rate of > or =1:8, with no differences related to the vaccine used for priming, whereas the anti Hib antibody concentration was higher in children primed with the MenC-TT (0.59; 95% CI: 0.49-0.71 vs. 0.39; 95% CI: 0.32-0.48).One month after the MenC vaccine booster 99.5% of the children had SBA > or =1:128. Children primed with MenC-TT reached higher SBA titers: 6520 (95% CI: 5359-7932) than those primed with MenC-CRM: 1903 (95% CI: 1600-2262). Children primed with MenC-CRM had SBA titers of 2061 (95% CI: 1599-2627) when boosted with MenC-TT and 1746 (95% CI: 1378-2213) when boosted with MenC-CRM. Children primed with MenC-TT had SBA titers of 6786 (95% CI: 5023-9167) and 6278 (95% CI: 4841-8144) when boosted with MenC-TT or MenC-CRM. There was no difference in the PRP antibody concentration after boosting. A booster MenC dose induces high SBA and anti Hib response with over 99% of children seroprotected. Children primed with a MenC-TT vaccine reached SBA titers 3.5 times higher no matter which vaccine was used for boosting.

Levels of Haemophilus influenzae type B (Hib) antibody in Turkey before routine immunization

The Haemophilus influenzae type b (Hib) vaccine was introduced into the routine immunization schedule in Turkey on January 1, 2007. This study investigates the immunity to Hib prior to the introduction of the vaccine. Materials and methods: Serum samples were collected from healthy volunteers between the ages of 6 months and 50 + years of age, living in the area of 26 health centers in the Samsun, Antalya, and Diyarbakir provinces during 2000-2001. In total, 1713 sera were selected for this study, and the younger age groups were given priority (range 0-82). A commercial ELISA test was used to measure anti-Hib IgG. Hib antibody concentrations of 0.15 to < 1.0, and >= 1.0 µg/mL were considered as non protective, short-term protection, and long term protection, respectively. The statistical analyses performed were the chi-square test and logistic regression. Results: The antibody levels considered non-protective were 58.0%, 35.3%, 28.1%, 19.8%, 18.4%, 15.3%, and 20.6% among < 5, 5-9, 10-19, 20-29, 30-39, 40-49, and 50 and over age groups, respectively. Protection against Hib infection increased by age in all 3 provinces. Conclusion: This study provides important baseline data on anti-Hib antibody levels in Turkey before routine immunization was introduced, and shows that there is a considerable percentage of subjects with non-protective antibody levels.

Antibody Response to Polysaccharide Conjugate Vaccines after Nonmyeloablative Allogeneic Stem Cell Transplantation

After allogeneic stem cell transplantation with reduced-intensity conditioning regimens (allo-RIST) patients are susceptible to bacterial and viral infections for a period that may last several years. The efficacy of the recommended vaccination schedules, in terms of induction of a protective antibody response, is unknown. In this study, the reconstitution of humoral immunity after allo-RIST is determined by measuring the vaccination-induced antibody response against Streptococcus pneumoniae, Haemophilus influenzae type b (Hib), and tetanus toxoid (TT) 1 year posttransplantation. Patients who underwent allo-RIST were vaccinated according to a schedule starting at 12 months following transplantation with conjugated vaccines against S. pneumoniae, Hib, and TT. Of twenty-six patients both pre- and postvaccination sera were available. Patients were required to be off immunosuppression at the time of vaccination, and, therefore, 9 of the 26 patients did not start vaccination at 12 months post-stem cell transplantation but rather at a median range of 15 (12-36 months) posttransplantation. Except for pneumococcal serotype 6B, more than 73% of the patients developed antibody levels >or=0.35 microg/mL for all pneumococcal serotypes included in the vaccine. For Hib and TT, protective antibody levels were found in 77% and 96% of the patients, respectively. Vaccination of patients at a median of 15 months post-allo-RIST leads to significant rise in concentrations of pneumococcal, Hib, and TT antibodies in the majority of patients.

The acquisition of anti-pneumococcal capsular polysaccharide Haemophilus influenzae type b and tetanus toxoid antibodies, with age, in the UK.

Antibody levels specific for capsular polysaccharides of Streptococcus pneumoniae and Haemophilus influenzae type b (Hib) and to tetanus toxoid (TT), were measured in serum samples of 750 age-stratified subjects from the UK. The study subjects comprised healthy adult volunteers and hospitalized children undergoing elective surgery, excluding those with a history of infection or under investigation for immunological or haematological disorders. These antibody levels were calibrated by comparison with serum pool obtained from healthy adult volunteers, who were immunized with Hib polyribose-phosphate vaccine (Merieux). The data are intended to provide reference ranges to assist in the interpretation of specific antibody measurements in the clinical setting. Maternal IgG pneumococcal capsular polysaccharide (PCP) specific antibody levels, geometric-mean titre (GMT) 1/22, were lost by 6 months of age (GMT of 1/9). They remained low until 3-5 years (GMT of 1/20), and consisted principally of IgG1. Thereafter, IgG anti-PCP antibody titres increased steadily to adult levels (GMT of 1/275), of which 80% was IgG2. Anti-PCP antibody titres of the IgM isotype rose steadily from a GMT 1/21 (0-6 months) to 1/420 (3-5 years), a level which was maintained until adulthood. Anti-Hib antibody concentrations, determined by RABA, again demonstrated the decline in maternal antibody, from 0.18 micrograms/ml in the 0-6 month age cohort, to 0.09 microgram/ml between 6 and 12 months. Geometric-mean antibody concentrations remained below 0.2 micrograms/ml until 3-5 years, then increased with age, attaining the mean adult level of 1.02 micrograms/ml. Anti-TT antibody concentrations were measured in the same sera, by ELISA. Two peaks in anti-TT antibody levels were seen in children of 0.059 IU/ml and 0.166 IU/ml corresponding to the schedule of routine childhood immunization in the first year and at 5 years of age.

The effect of ranitidine on antibody responses to polysaccharide vaccines in patients with B‐cell chronic lymphocytic leukaemia

To analyse the effects of ranitidine treatment on vaccination induced antibody responses in patients with chronic lymphocytic leukaemia (CLL). Fifty CLL patients were vaccinated with tetanus conjugated Hib vaccine and a 23-valent pneumococcal polysaccharide vaccine with (n = 25) or without (n = 25) ranitidine treatment in a matched case--control setting. Anti tetanus toxoid (TT), anti-Hib and anti-pneumococcal antibody levels were determined before and after vaccination. Additionally, cytokine levels were assessed in patients treated with ranitidine. Vaccination-induced increases in anti-Hib and anti-TT antibody levels were higher in the ranitidine group compared with the control group. Anti-pneumococcal antibody responses were not improved by administration of ranitidine. Higher levels of IL-18 were found in patients treated with ranitidine compared with healthy controls. Levels of IL-6, IL-8, IL-18, RANTES, IP-10, sVCAM-1 and sICAM-1 were within normal ranges and did not change during ranitidine treatment. Ranitidine treatment improves vaccination-induced T-cell dependent antibody responses in patients with CLL but has no beneficial effect on the response to vaccination with unconjugated polysaccharide antigens.

Immunogenicity and effectiveness of Haemophilus influenzae type b conjugate vaccine in HIV infected and uninfected African children

The quantitative (anti-Hib capsular polysaccharide antibody concentrations; anti-HibPS) and qualitative (bactericidal activity and avidity) aspects in immune responses to Haemophilus influenzae type b polyribosyl ribitol phospshate-CRM 197 conjugate vaccine (HibCV; HibTiter ®) were evaluated in 66 HIV infected children not receiving anti-retroviral therapy and 127 HIV uninfected children. Surveillance was conducted for invasive Hib disease in a cohort of 39 865 (approximately 6.4% of whom were HIV infected) children from March 1998 to June 2004. HIV infected children had lower anti-HibPS geometric mean antibody concentrations 1 month post-immunisation than HIV uninfected children ( P < 0.00001) and were less likely to have anti-HibPS antibody concentrations of ≥1.0 μg/ml (RR 0.54; 95% CI 0.43–0.69). A lower proportion of HIV infected children than HIV uninfected children (RR 0.78; 95% CI 0.66–0.93) had measurable anti-Hib serum bactericidal activity (SBA) and the HibPS antibody concentration required for 50% killing of Hib bacteria was greater among HIV infected than HIV uninfected children ( P = 0.001). The estimated risk of HibCV failure was 35.1-fold greater (95% CI 14.6–84.6) amongst HIV infected than HIV uninfected children.

Immunogenicity and Tolerability of a Heptavalent Pneumococcal Conjugate Vaccine Administered at 3, 5 and 12 Months of Age

The recommended vaccination schedule for the pneumococcal conjugate vaccine (PCV) includes 4 immunizations, according to the national programs in the United States and some European countries. Other countries use a national schedule for routine vaccinations in early childhood that includes only 3 doses. The goals were to assess the immunogenicity and tolerability of PCV with a vaccination schedule that included 3 doses during the first 1 year of life (a 2+1 dose schedule) and to determine the immune responses to concomitantly administered Haemophilus influenzae type b (Hib) vaccine. A total of 101 healthy Swedish infants were enrolled in an open, nonrandomized, multicenter study. PCV was administered concomitantly with (at separate sites) a diphtheria-tetanus toxoids-acellular pertussis vaccine, inactivated polio vaccine and Hib conjugate vaccine combination at 3, 5 and 12 months of age. IgG antibody concentrations for the 7 serotypes included in the PCV and the Hib capsular polysaccharide in serum samples taken at 3, 6, 12 and 13 months were determined with enzyme immunoassays. Local and systemic reactions were monitored for 3 days after each immunization, and serious adverse reactions were monitored for the whole study period. Two doses of PCV induced satisfactory antibody responses, with the exception of serotypes 6B and 23F. The third dose evoked strong responses for all serotypes, which suggests good immunologic priming with the primary series of 2 doses. The mean anti-Hib antibody concentrations were similar to those noted in earlier studies among Swedish children. The PCV was well tolerated. The pneumococcal antibody concentrations at 13 months were comparable with those noted previously with the 4-dose schedule. The results suggest that the implementation of a 2+1 dose schedule for PCV should be considered.