Impact of conjugate Haemophilus influenzae type b (Hib) vaccine introduction in South Africa

OBJECTIVE: To analyse trends in reported invasive Haemophilus influenzae disease in South Africa within the first five years of introduction of conjugate Haemophilus influenzae type b (Hib) vaccine in the routine child immunization schedule. METHODS: We used national laboratory-based surveillance data to identify cases of invasive H. influenzae disease between July 1999 and June 2004, and submitted isolates for serotyping and antimicrobial susceptibility testing. FINDINGS: The absolute number of Hib cases (reported to the national surveillance system) among children below one year of age decreased by 65%, from 55 cases in 1999-2000 to 19 cases in 2003-04. Enhanced surveillance initiated in 2003, identified human immunodeficiency virus (HIV)-infection and incomplete vaccination as contributing factors for Hib transmission. The total number of laboratory-confirmed cases of H. influenzae remained unchanged because non-type b disease was being increasingly reported to the surveillance system concomitant with system enhancements. Children with non-typable disease were more likely to be HIV-positive (32 of 34, 94%) than children with Hib disease (10 of 14, 71%), P = 0.051. Recent Hib isolates were more likely to be multidrug resistant (2% in 1999-2000 versus 19% in 2003-04, P = 0.001). CONCLUSION: Data from a newly established national laboratory-based surveillance system showed a decrease in Hib disease burden among South African children following conjugate vaccine introduction and identified cases of non-typable disease associated with HIV infection.     

Re-emergence of Haemophilus influenzae type b (Hib) disease in The Gambia following successful elimination with conjugate Hib vaccine

Invasive Hib disease, which remains a major cause of childhood mortality and morbidity in most of the developing world, was eliminated in The Gambia by 2002 following the introduction of conjugate Hib vaccine in 1997. Formal disease surveillance was stopped in 2002 but five cases (including three of meningitis) were detected non-systematically between July 2005 and April 2006. This equates to an incidence of 3 per 100,000 annually for meningitis, a likely underestimate. The age distribution of cases (median 15 months, range 0-36 months) was older than previously seen and there were examples of apparent vaccine failure, but the cause for this re-emergence is not clear. No evidence was found of the emergence of a hypervirulent strain. The re-establishment of continuing surveillance is required to answer the questions raised by this report, and is particularly important in settings like The Gambia, where a booster dose is not given, to determine long-term effects of national immunisation with Hib vaccine.     

Haemophilus influenzae meningitis 5 years after introduction of the Haemophilus influenzae type b conjugate vaccine in Brazil

The long-term impact of Haemophilus influenzae type b (Hib) conjugate vaccine, introduced throughout Latin America in the late 1990s, has not been evaluated. Active surveillance for H. influenzae meningitis was performed from August 9, 1996 to August 8, 2004 in Metropolitan Salvador, Brazil. Five years after the introduction of Hib conjugate vaccine, Hib meningitis incidence decreased from 2.39 to 0.06 cases per 100,000 population (98%) overall, and from 60.9 to 3.1 cases per 100,000 population (95%) in children <1 year of age. A transient serotype replacement phenomenon was observed associated with a small increase of meningitis due to two H. influenzae type a clonal groups. These findings indicate that Hib immunization campaign has led to the virtual elimination of Hib disease in this region.     

Impact of routine vaccination with a conjugate Haemophilus influenzae type b vaccine

Based on a unique nationwide registration of vaccinated children, we studied the impact of routine Hib vaccination with special emphasis on vaccine uptake and adherence, vaccine effectiveness with respect to Hib meningitis, and indirect effects with respect to Hib meningitis among the unvaccinated children. Uptake and adherence was generally satisfactory. We estimated >97% effectiveness for all three doses of vaccine and observed herd-immunity in unvaccinated children comparable to a vaccine effectiveness of 94% 3.5 years into the programme. In conclusion, nationwide routine Hib vaccination is highly effective in protecting against Hib meningitis, and rapid achievement of herd immunity is possible with catch-up vaccination of older children.     

Safety of a combination diphtheria, tetanus toxoid, acellular pertussis, hepatitis B, and inactivated polio vaccine coadministered with a 7-valent pneumococcal conjugate vaccine and a Haemophilus influenzae type b conjugate vaccine

The safety of DTaP-HepB-IPV vaccine coadministered with PCV and Hib was compared with separate administration of DTaP, HepB, IPV, Hib, and PCV at 2, 4, and 6 months of age. Healthy 2-month-old infants (N=1008) were randomized to the two groups. Following dose 1, there was no significant difference between the groups in the incidence of fever >101.3 degrees F. After each dose, the incidence of any fever (> or =100.4 degrees F) was significantly higher in the Combination Vaccine Group. The rate of fever >103.1 degrees F was < or =1.4% in both groups after any of the doses. Medical advice visits for fever were infrequent in both groups (< or =1.2%). DTaP-HepB-IPV was safe and well tolerated when coadministered with PCV and Hib.     

2015-2017年湖北省含B型流感嗜血杆菌成分疫苗安全性分析

目的 分析2015-2017年湖北省3种含B型流感嗜血杆菌成分疫苗的疑似预防接种异常反应(adverse events following immunization,AEFI)发生特征,评价预防接种安全性。方法 收集2015-2017年湖北省在中国AEFI信息管理系统接种报告的B型流感嗜血杆菌结合疫苗(Hib)、DTaP-b型流感嗜血杆菌联合疫苗(DTaP-Hib)与DTaP-灭活脊髓灰质炎-b型流感嗜血杆菌联合疫苗(DTaP-IPV/Hib)个案数据,采用描述性流行病学方法分析。结果 2015-2017年湖北省共报告含B型流感嗜血杆菌成分疫苗的AEFI 1391例(50.80/10万剂),其中一般反应1276例(46.60/10万剂),异常反应100例(3.65/10万剂);Hib、DTaP-Hib、DTaP-IPV/Hib 3种疫苗的AEFI分别为753例(37.40/10万剂)、354例(88.41/10万剂)、284例(87.56/10万剂)。DTaP-Hib和DTaP-IPV/Hib疫苗一般反应报告发生率高于Hib疫苗一般反应报告发生率;3种疫苗加强免疫报告发生率高于基础免疫报告发生率。3种疫苗一般反应均以发热(27.61/10万剂)、局部红肿(21.51/10万剂)、局部硬结(10.19/10万剂)为主;异常反应主要为过敏性皮疹(3.36/10万剂)。结论 含B型流感嗜血杆菌成分的3种疫苗AEFI报告发生率较低,均具有良好的安全性。     

Preparation and testing of a Haemophilus influenzae Type b/Hepatitis B surface antigen conjugate vaccine

The majority of conjugate vaccines focus on inducing an antibody response to the polysaccharide antigen and the carrier protein is present primarily to induce a T-cell dependent response. In this study conjugates consisting of poly(ribosylribitolphosphate) (PRP) purified from Haemophilus influenzae Type b bound to Hepatitis B virus surface antigen (HBsAg) virus like particles were prepared with the aim of inducing an antibody response to not only the PRP but also the HBsAg. A conjugate consisting of PRP bound to HBsAg via an adipic acid dihydrazide (ADH) spacer induced strong IgG antibodies to both the PRP and HBsAg. When conjugation was performed without the ADH spacer the induction of an anti-PRP response was equivalent to that seen by conjugate with the ADH spacer, however, a negligible anti-HBsAg response was induced. For comparison, PRP was conjugated to diphtheria toxoid (DT) and Vi polysaccharide purified from Salmonella Typhi conjugated to HBsAg both using an ADH spacer. The PRP_AH–DT conjugate induced strong anti-PRP and anti-DT responses, the Vi–_AHHBsAg conjugate induced a good anti-HBsAg response but not as strong as that induced by the PRP_AH–HBsAg conjugate. This study demonstrated that in mice it was possible to induce robust antibody responses to both polysaccharide and carrier protein provided the conjugate has certain physico-chemical properties. A PRP_AH–HBsAg conjugate with the capacity to induce anti-PRP and anti-HBsAg responses could be incorporated into a multivalent pediatric vaccine and simplify formulation of such a vaccine.     

Haemophilus influenzae type b vaccination and risk of childhood leukemia in a vaccine trial in finland

PURPOSE: To compare the incidence of childhood leukemia among children who received multiple early vaccine doses versus a single late dose in the context of a clinical trial in Finland during 1986 and 1987.METHODS: The trial was offered to the parents of all 114,000 children born in Finland between October 1, 1985 and August 31, 1987; 98% of the eligible children were enrolled. The vaccine consisted of heat-sized capsular polysaccharide of Haemophilus influenzae type b (Hib) coupled to diptheria toxoid (PRP-D). Children with odd birth dates received four doses of the vaccine at the ages of 3, 4, 6, and 14 months; children with even birth dates received only one dose, at the age of 24 months. The numbers of boys and girls with even and odd birth dates during the window of eligibility who remained alive during the follow-up period were obtained from the Finnish Population Registry. Numbers of leukemia cases diagnosed through 1996 among children with even and odd birth dates during the window of eligibility were obtained from the Finnish Cancer Registry. Poisson regression analysis of leukaemia incidence rates was conducted using the number of cases as the outcome variable and the natural logarithm of number of children at risk as an offset term. For comparison of the early and late vaccination groups, a binary variable based on odd or even date of birth was used.RESULTS: Among the 114,000 subjects, a total of 77 cases of childhood leukaemia were diagnosed: 33 in the early-vaccination group and 44 in the late-vaccination group. The incidence of childhood leukaemia was lower in the early-vaccination group (relative risk 0.72, 95% confidence interval 0.46-1.13) than in the late-vaccination group, but the difference did not reach statistical significance.CONCLUSIONS: Our results suggest that early vaccination against Hib may reduce the incidence of childhood leukaemia, but confirmatory studies are needed.     

Estimation of the indirect effect of Haemophilus influenzae type b conjugate vaccine in an American Indian population

BACKGROUND: Oropharyngeal carriage studies of Haemophilus influenzae type b (Hib) and the rapid drop in Hib invasive disease in countries with widespread Hib conjugate vaccine immunization programmes for infants have indicated there may be significant indirect effects (herd immunity) associated with these vaccines. Our goal was to quantify the magnitude of these effects in an American Indian population during its early years of Hib immunization. METHODS: In a synthetic case-cohort study, we combined data from an efficacy trial, an immunization uptake records survey, and ongoing surveillance for Hib disease on the Navajo Nation from 1988 to 1992. Decline in the incidence of invasive Hib disease among children <2 years old was estimated via proportional hazards survival models as a function of individual immunization status and the proportion of immunized children in a community. RESULTS: The predominant vaccine during the study period was Hib-OMPC (92% of immunizations). The effectiveness of receipt of at least one dose was 97.2%. Compared to communities with 0-20% coverage with at least one dose, residence in communities with 20-40% and 40-60% coverage was associated with risk reductions of 56.5% and 73.2%, respectively. CONCLUSIONS: The results indicate substantial indirect effects of Hib-OMPC immunization may occur even at relatively low levels of immunization coverage. Countries that implement Hib immunization programmes may receive greater benefits at the community level than those due to the direct protection conferred to the individual through vaccination.     

Effectiveness of pneumococcal Haemophilus influenzae protein D conjugate vaccine against pneumonia in children: A cluster-randomised trial

BackgroundPneumococcal conjugate vaccines have potential to prevent significant proportion of childhood pneumonia. Finnish Invasive Pneumococcal disease vaccine trial was designed to assess the vaccine effectiveness (VE) of the 10-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against several outcomes. We now report results for pneumonia.MethodsIn this nationwide, cluster-randomised, double-blind trial, children younger than 19 months received PHiD-CV10 in 52 clusters or hepatitis vaccines as control in 26 clusters. Infants younger than 7 months at the first vaccination received either 3+1 or 2+1 vaccination schedule, children aged 7–11 months received 2+1, and those 12–18 months of age two-dose schedule. All hospitalizations and outpatient visits to hospital associated with ICD-10 codes compatible with pneumonia were identified through the National Care Register and 1–3 frontal chest X-ray images per event were collected. External readers who were unaware of the patients’ vaccination status retrospectively interpreted the images. The evaluated outcomes were hospital-diagnosed, hospital-treated pneumonia as primary diagnosis, and radiologically confirmed pneumonia during the blinded, intention-to-treat follow-up period from the first vaccination to the end of 2011. Total VE was calculated as 1 minus rate ratio of all pneumonia episodes.Results47 366 children were enrolled from February 2009, to October 2010. VE against all episodes of hospital-diagnosed pneumonia was 27% (95% confidence interval [CI]: 14%, 38%), 32% (95% CI: 3%, 52%), and 23% (95% CI: −5%, 44%) in subjects enrolled at age <7, 7–11, and 12–18 months, respectively. Corresponding rate reductions were 3.4, 4.7, and 2.5 per 1000 person-years. VE estimates against pneumonia with alveolar consolidation or pleural effusion (WHO criteria) in the three cohorts were 45% (95% CI: 26%, 60%), 56% (95% CI: 14%, 77%), and 48% (95% CI: 2%, 73%), respectively.ConclusionPHiD-CV10 vaccination remarkably reduced disease burden due to pneumonia in infants and young children.Clinical trial registrationMain trial NCT00861380, nested carriage and otitis media trial NCT00839254 (ClinicalTrials.gov).     

Economic evaluation of Haemophilus influenzae type B vaccination in Indonesia: a cost-effectiveness analysis

BACKGROUND: Haemophilus influenzae type B (Hib) causes significant morbidity and mortality in children under five years of age. A safe and effective vaccine is available but is not in general use in developing countries. This paper evaluates the cost-effectiveness of introducing Hib vaccine in Indonesia as an addition to the country's current DTP-Hepatitis B vaccination program. METHODS: The economic analysis uses a societal perspective and is based on a 1-year birth cohort of 4.234 million. The disease status of children with and without Hib vaccination is modeled for the year, and health consequences are modeled over the expected life of the child. One-way, two-way, probabilistic and worst-case sensitivity analyses were performed to evaluate the robustness of the results. RESULTS: Implementation of Hib vaccination in Indonesia would avert approximately 76,700 cases of invasive infection, more than 7,150 deaths and 273,000 disability-adjusted life years (DALYs). Compared to no vaccine, the incremental cost-effectiveness ratio (ICER) is US $67 per DALY averted based on UNICEF pricing, whereas the program would save US $3.7 million with GAVI pricing. The result is not sensitive to uncertainty in disease incidence, costs of treatment or the probability of developing immunity. CONCLUSION: The model demonstrates significant cost-effectiveness of implementation of a Hib vaccination program for Indonesian society.     

Haemophilus influenzae type b conjugate vaccine stability: catalytic depolymerization of PRP in the presence of aluminum hydroxide

The structural stability of the Haemophilus influenzae type b (Hib) capsular polysaccharide, polyribosylribitolphosphate (PRP) in an aluminum hydroxide adsorbed, polysaccharide-protein conjugate vaccine was monitored using modifications of an HPLC assay developed by Tsai et al. [Tsai C-M, Gu X-X, Byrd RA. Quantification of polysaccharide in Haemophilus influenzae type b conjugate and polysaccharide vaccines by high-performance anion-exchange chromatography with pulsed amperometric detection. Vaccine 1993;12:700-706.]. As applied to products containing PRP conjugated to the outer membrane protein complex (OMPC) from Neisseria meningitidis, this assay allows direct measurement of the total PRP content in very complex samples including commercial vaccine products. In addition, with the use of a high-speed centrifugation step, the assay can be used to directly quantify any PRP that is not conjugated to the OMPC carrier protein. These results provide evidence of what appears to be a catalytic reaction taking place between the phosphodiester bond of PRP and the aluminum hydroxide adjuvant that results in hydrolysis of the PRP polymer into smaller chain lengths and liberation of PRP oligomers from the conjugate particle. The reaction approaches an asymptotic limit after approximately two years at 2-8 degrees C. Clinical studies which span this time period confirm that the modest decrease in conjugated PRP content over time does not impact the overall clinical effectiveness of PRP-OMPC-containing vaccines.     

Impact of the introduction of the Haemophilus influenzae type b conjugate vaccine in an urban setting in southern India

Introduction

Haemophilus influenzae type b was the leading cause of bacterial meningitis in infants and children below the age of two years prior to the introduction of H. influenzae type b conjugate vaccines. In December 2011, the Indian government introduced H. influenzae b vaccine in the state of Tamilnadu. A prospective surveillance for bacterial meningitis was established at the Institute of Child Health in Chennai to evaluate the etiology of meningitis and impact of the vaccine.

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 >or=1.0 microg/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.     

Mortality from meningococcal disease during an epidemic in The Gambia, West Africa

Mortality from meningococcal disease was determined during an epidemic in a rural area of The Gambia with few medical resources, but where a system of registration of births and deaths had been established before the introduction of a primary health care programme. 33 deaths were recorded among 127 patients, a case mortality rate of 26%. 84% of deaths occurred within the first 24 h of illness and many patients died before they could reach any source of treatment. Previous studies, based on regional statistics or on hospital series, may have underestimated mortality from epidemic meningitis in Africa. Mortality from this infection will be reduced only if treatment can be made readily accessible to patients early in the course of their illness.     

Response of MUTZ-3 dendritic cells to the different components of the Haemophilus influenzae type B conjugate vaccine: towards an in vitro assay for vaccine immunogenicity

Potency testing is mandatory for vaccine registration and batch release. Due to various limitations to in vivo potency testing, there is need for relevant in vitro alternatives. These alternative tests should preferably comprise cells from the target (human) species. The whole suite of immune responses to vaccination that occur in vivo in humans cannot be tested in vitro using a single cell type. Even so, dendritic cells (DC) form an important candidate cell type since they are pivotal in inducing and orchestrating immune responses. Cell lines are preferred over ex vivo cells for reasons of safety, accessibility, and reproducibility. In this first feasibility study we used the human cell line MUTZ-3, because it most closely resembles ex vivo human DC, and compared its response to monocyte-derived DC (moDC).Haemophilus influenzae type B (HiB) vaccine was chosen because its components exert different effects in vivo: while the HiB antigen, polyribosyl ribitol phosphate (PRP) fails to induce sufficient protection in children below 2 years of age, conjugation of this polysaccharide antigen to outer membrane protein (OMP) of Neisseria meningitides, results in sufficient protection. Effects of PRP, OMP, conjugated PRP-OMP, and adjuvanted vaccine (PedVax HiB), on cytokine production and surface marker expression were established. PRP induced no effects on cytokine production and the effect on surface marker expression was limited to a minor decrease in CD209 (DC-SIGN). In both MUTZ-3 and moDC, OMP induced the strongest response both in cytokine production and surface marker expression. Compared to OMP alone conjugated PRP-OMP generally induced a weaker response in cytokine production and surface marker expression. The effects of PedVax HiB were comparable to conjugated PRP-OMP. While moDC showed a larger dynamic range than MUTZ-3 DC, these cells also showed considerable variability between donors, with MUTZ-3 DC showing a consistent response between the replicate assays. In our view, this makes MUTZ-3 DC the cells of choice. In conclusion, our results demonstrate that the MUTZ-3 DC assay allows discrimination between compounds with different immunogenicity. The potential of this cell line as (part of) an in vitro immunogenicity assay should be further explored.     

The impact of routine infant immunization with Haemophilus influenzae type b conjugate vaccine in Malawi, a country with high human immunodeficiency virus prevalence

Malawi has extreme poverty and a high-human immunodeficiency virus (HIV) prevalence. Following Haemophilus influenzae type b (Hib) conjugate vaccine introduction during 2002, we evaluated vaccine impact by reviewing hospital surveillance data for acute bacterial meningitis in Blantyre district among children age 1-59 months admitted during 1997-2005. Documented annual Hib meningitis incidence rates decreased from 20-40/100,000 to near zero among both rural and urban residents despite no change in pneumococcal meningitis incidence rates. Before vaccine introduction, an average of 10 children/year had Hib meningitis and HIV infection compared to 2/year during 2003-2004 and none during 2005. Vaccine effectiveness was high following two or more doses of vaccine. The most urgent future need is for a sustainable routine infant immunization program, including a less expensive vaccine that preferably is delivered in a multivalent form.     

Therapeutic landscapes of the Jola, The Gambia, West Africa

This paper contributes to the 'new' medical geography through its analysis of the therapeutic landscapes of the Jola of The Gambia. The paper advances the debate surrounding the conceptualization of medicine and health through a review of literature on African medicinal systems; it examines in detail the health care system of the Jola of The Gambia, documenting indigenous human and ethnoveterinary medical beliefs and practices and focusing in particular on the role of herbal medicine; and it discusses the interactions and links between indigenous medicine and biomedicine, thus demonstrating the importance of placing an understanding of health care systems in different places within an awareness of global power relations. The paper therefore links cultural perspectives with a political economy analysis, to highlight the importance of place and specificity of cultural context when investigating health care beliefs and practices. The intention of the paper is to present a theoretically informed empirical case study which reinforces the practical value of a 'new' medical geography.     

Economic evaluation of delivering Haemophilus influenzae type b vaccine in routine immunization services in Kenya

OBJECTIVE: Haemophilus influenzae type b (Hib) vaccine was introduced into routine immunization services in Kenya in 2001. We aimed to estimate the cost-effectiveness of Hib vaccine delivery. METHODS: A model was developed to follow the Kenyan 2004 birth cohort until death, with and without Hib vaccine. Incidence of invasive Hib disease was estimated at Kilifi District Hospital and in the surrounding demographic surveillance system in coastal Kenya. National Hib disease incidence was estimated by adjusting incidence observed by passive hospital surveillance using assumptions about access to care. Case fatality rates were also assumed dependent on access to care. A price of US$ 3.65 per dose of pentavalent diphtheria-tetanus-pertussis-hep B-Hib vaccine was used. Multivariate Monte Carlo simulations were performed in order to assess the impact on the cost-effectiveness ratios of uncertainty in parameter values. FINDINGS: The introduction of Hib vaccine reduced the estimated incidence of Hib meningitis per 100,000 children aged < 5 years from 71 to 8; of Hib non-meningitic invasive disease from 61 to 7; and of non-bacteraemic Hib pneumonia from 296 to 34. The costs per discounted disability adjusted life year (DALY) and per discounted death averted were US$ 38 (95% confidence interval, CI: 26-63) and US$ 1197 (95% CI: 814-2021) respectively. Most of the uncertainty in the results was due to uncertain access to care parameters. The break-even pentavalent vaccine price--where incremental Hib vaccination costs equal treatment costs averted from Hib disease--was US$ 1.82 per dose. CONCLUSION: Hib vaccine is a highly cost-effective intervention in Kenya. It would be cost-saving if the vaccine price was below half of its present level.