Effectiveness of Haemophilus influenzae type b vaccines administered according to various schedules: systematic review and meta-analysis of observational data

The Promising Potential of Reverse Vaccinology-Based Next-Generation Vaccine Development over Conventional Vaccines against Antibiotic-Resistant Bacteria

The clinical use of antibiotics has led to the emergence of multidrug-resistant (MDR) bacteria, leading to the current antibiotic resistance crisis. To address this issue, next-generation vaccines are being developed to prevent antimicrobial resistance caused by MDR bacteria. Traditional vaccine platforms, such as inactivated vaccines (IVs) and live attenuated vaccines (LAVs), were effective in preventing bacterial infections. However, they have shown reduced efficacy against emerging antibiotic-resistant bacteria, including MDR M. tuberculosis. Additionally, the large-scale production of LAVs and IVs requires the growth of live pathogenic microorganisms. A more promising approach for the accelerated development of vaccines against antibiotic-resistant bacteria involves the use of in silico immunoinformatics techniques and reverse vaccinology. The bioinformatics approach can identify highly conserved antigenic targets capable of providing broader protection against emerging drug-resistant bacteria. Multi-epitope vaccines, such as recombinant protein-, DNA-, or mRNA-based vaccines, which incorporate several antigenic targets, offer the potential for accelerated development timelines. This review evaluates the potential of next-generation vaccine development based on the reverse vaccinology approach and highlights the development of safe and immunogenic vaccines through relevant examples from successful preclinical and clinical studies.

Biomarkers detected in cord blood predict vaccine responses in young infants

Introduction

Factors influencing vaccine immune priming in the first year of life involve both innate and adaptive immunity but there are gaps in understanding how these factors sustain vaccine antibody levels in healthy infants. The hypothesis was that bioprofiles associated with B cell survival best predict sustained vaccine IgG levels at one year.

Methods

Longitudinal study of plasma bioprofiles in 82 term, healthy infants, who received standard recommended immunizations in the United States, with changes in 15 plasma biomarker concentrations and B cell subsets associated with germinal center development monitored at birth, soon after completion of the initial vaccine series at 6 months, and prior to the 12-month vaccinations. Post vaccination antibody IgG levels to Bordetella pertussis, tetanus toxoid, and conjugated Haemophilus influenzae type B (HiB) were outcome measures.

Results

Using a least absolute shrinkage and selection operator (lasso) regression model, cord blood (CB) plasma IL-2, IL-17A, IL-31, and soluble CD14 (sCD14) were positively associated with pertussis IgG levels at 12 months, while CB plasma concentrations of APRIL and IL-33 were negatively associated. In contrast, CB concentrations of sCD14 and APRIL were positively associated with sustained tetanus IgG levels. A separate cross-sectional analysis of 18 mother/newborn pairs indicated that CB biomarkers were not due to transplacental transfer, but rather due to immune activation at the fetal/maternal interface. Elevated percentages of cord blood switched memory B cells were positively associated with 12-month HiB IgG levels. BAFF concentrations at 6 and 12 months were positively associated with pertussis and HiB IgG levels respectively.

Discussion

Sustained B cell immunity is highly influenced by early life immune dynamics beginning prior to birth. The findings provide important insights into how germinal center development shapes vaccine responses in healthy infants and provide a foundation for studies of conditions that impair infant immune development.

Trends of global and regional aetiologies, risk factors and mortality of lower respiratory infections from 1990 to 2019: An analysis for the Global Burden of Disease Study 2019

BACKGROUND AND OBJECTIVE

Lower respiratory infections (LRIs) are a leading cause of death worldwide. We aimed to estimate the trends of global and regional aetiologies, risk factors and mortality of LRIs from 1990 to 2019.

METHODS

From the Global Burden of Disease (GBD) Study 2019, we collected relevant data, including annual LRI deaths, mortality and deaths and mortality attributable to the four high-burden aetiologies and 14 risk factors during 1990-2019. To quantify the temporal trends, estimated annual percentage changes (EAPCs) were calculated by fitting linear regression model.

RESULTS

Globally, the age-standardized mortality due to LRIs decreased by an average of 2.39% (95% CI 2.33%-2.45%) per year, from 66.67 deaths per 100,000 in 1990 to 35.72 deaths per 100,000 in 2019. Low Socio-demographic Index regions, South Asia and Sub-Saharan Africa had the heaviest burden of LRIs. The age-standardized mortality decreased in 18 GBD regions, whereas increased in Southern Latin America (EAPC = 1.20, 95% CI 1.03-1.37). LRIs led to considerable deaths among children under 5 years and adults older than 70 years. Streptococcus pneumoniae was the first leading aetiology, accounting for over 50% of LRI deaths. Household air pollution from solid fuels, child wasting and ambient particulate matter pollution were the three leading risk factors for LRI mortality in 2019.

CONCLUSION

LRIs remain an important health problem globally, especially in some vulnerable areas and among children under 5 and adults over 70 years. Future researches focusing on the aetiologies and risk factors for LRIs are needed to provide targeted and updated prevention strategies.

Theories-based determinants analysis of Hib-combined vaccine hesitancy in China: A multi-group structural equation modeling

OBJECTIVES

To explore determinants of Hib-combined vaccine hesitancy in Chinese parents, and to provide scientific intervention measures to tackle vaccine hesitancy.

METHODS

2,531 parents were recruited from local healthcare centers in Zhejiang Province by accidental sampling, and completed the self-developed online questionnaire with voluntary participation. Health Belief Model and Model of Determinants of Vaccine Hesitancy were applied to construct the framework of research. Multi-group Structural Equation Modeling was performed to explore the effects of determinants of vaccine hesitancy across various socio-economic status (SES).

RESULTS

Hib-combined vaccine hesitancy for total sample was 2.184 ± 0.777 (95%CI: 2.153-2.214), and most of them were in low (n = 1436, 56.7%) level. Low SES group (2.335 ± 0.763, 95%CI: 2.271-2.400) had significantly highest vaccine hesitancy. For total sample, Self-Efficacy and Cues to Action presented -0.517 and -0.437 of standard total effect on Vaccine Hesitancy, respectively. The Multi-group Structural Equation Model with satisfying goodness of fit in SES groups (χ2 = 1616.074, df = 314, χ2/df = 5.147, CFI = 0.973, TLI = 0.966, SRMR = 0.027, RMSEA = 0.041) showed that Cues to Action imposed -0.621 (95%CI: -0.867-0.389, p < .001) of major standard total effect on Vaccine Hesitancy in low SES group, while Self-Efficacy imposed -0.560 (95%CI: -0.668-0.444, p < .001) and -0.685 (95%CI: -0.841-0.454, p < .001) of principal standard total effect on Vaccine Hesitancy in middle and high SES groups, respectively.

CONCLUSIONS

Hib-combined vaccine hesitancy in Chinese parents was low, and the lower the SES, the higher the vaccine hesitancy. Cues to Action and Self-Efficacy played primary role in declining vaccine hesitancy for parents at low SES, and at middle and high SES, respectively.

Typeable ampicillin-resistant Haemophilus influenzae strains in Tunisian's children

BACKGROUND

Here, we report the frequency of capsulated ampicillin-resistant Haemophilus influenzae strains isolated from children in Tunisia, particularly capsular serotype b, by polymerase chain reaction (PCR) to determine the molecular mechanisms underlying ampicillin resistance.

METHODS

We considered 22 capsulated H influenzae strains selected from a series of 91 ampicillin-resistant H influenzae strains isolated from children between 2010 and 2011 in Tunisia. The capsular serotypes of these strains were identified by slide agglutination and PCR.

RESULTS

By PCR, 19 (20.88%) serotype b, 1 (1.1%) serotype a, 2 (2.2%) serotypes d and f and 69 (75.82%) non-typeable strains were found among the 91 ampicillin-resistant H influenzae strains. 100% of the assumption between the consequences of antigenic examinations and PCR was found. The serotype b strains showed biotypes I, II, III, IV, VI, and VIII. The other capsulated strains showed biotypes IV and VIII. Thirteen of the serotype b strains created β-lactamase (14.28%). The 19 serotype b ampicillin-resistant H influenzae strains were subdivided into 3 bunches as indicated: The gathering of the β-lactamase positive, ampicillin-resistant where 11 strains (57.89%) were β-lactamase positive blaTEM-1 (+) and ftsI (+). The second gathering of the β-lactamase negative, ampicillin-resistant strains, where 6 isolates (31.58%) were β-lactamase negative blaTEM-1 (-) and ftsI (-), and lastly, the gathering of the β-lactamase positive, amoxicillin-clavulanate resistant where 2 isolates (10.52%) were β-lactamase positive blaTEM-1 (+) and ftsI (-).

CONCLUSION

PCR should be used in our country because it may contribute to decreasing the probability of transmission of these strains, especially those showing the two mechanisms of resistance among children in Tunisia.

Potential Application of Exosomes in Vaccine Development and Delivery

Exosomes are cell-derived components composed of proteins, lipid, genetic information, cytokines, and growth factors. They play a vital role in immune modulation, cell-cell communication, and response to inflammation. Immune modulation has downstream effects on the regeneration of damaged tissue, promoting survival and repair of damaged resident cells, and promoting the tumor microenvironment via growth factors, antigens, and signaling molecules. On top of carrying biological messengers like mRNAs, miRNAs, fragmented DNA, disease antigens, and proteins, exosomes modulate internal cell environments that promote downstream cell signaling pathways to facilitate different disease progression and induce anti-tumoral effects. In this review, we have summarized how vaccines modulate our immune response in the context of cancer and infectious diseases and the potential of exosomes as vaccine delivery vehicles. Both pre-clinical and clinical studies show that exosomes play a decisive role in processes like angiogenesis, prognosis, tumor growth metastasis, stromal cell activation, intercellular communication, maintaining cellular and systematic homeostasis, and antigen-specific T- and B cell responses. This critical review summarizes the advancement of exosome based vaccine development and delivery, and this comprehensive review can be used as a valuable reference for the broader delivery science community.

Hib Vaccines: Their Impact on Haemophilus influenzae Type b Disease

Haemophilus influenzae serotype b (Hib) is an important cause of serious, invasive infections, particularly in young children. Since 1985, a series of vaccines composed of the type b capsular polysaccharide polyribosylribitol phosphate (PRP), followed by PRP conjugated to various proteins, have been licensed for use in the United States and worldwide. The conjugated vaccines offer increased immunogenicity and prolonged durability of immune protection compared to the plain PRP vaccine and increasingly are combined with other childhood vaccines for decreased cost and increased ease of vaccination. Hib vaccines have a very favorable safety profile, have been found to be either cost-saving or cost-effective by many public health agencies, and, in most countries, are initiated during early infancy as part of routine childhood immunization programs. As a result of widespread use of the vaccines, the incidence of Hib infections, and their associated morbidity and mortality, has fallen dramatically across the globe. Yet, many children remain unimmunized or underimmunized against Hib, particularly in limited-resource countries. Future efforts to further reduce the disease burden of Hib infections remain a high priority.

Invasive Haemophilus influenzae Infections after 3 Decades of Hib Protein Conjugate Vaccine Use

Haemophilus influenzae serotype b (Hib) was previously the most common cause of bacterial meningitis and an important etiologic agent of pneumonia in children aged <5 years. Its major virulence factor is the polyribosyl ribitol phosphate (PRP) polysaccharide capsule. In the 1980s, PRP-protein conjugate Hib vaccines were developed and are now included in almost all national immunization programs, achieving a sustained decline in invasive Hib infections. However, invasive Hib disease has not yet been eliminated in countries with low vaccine coverage, and sporadic outbreaks of Hib infection still occur occasionally in countries with high vaccine coverage. Over the past 2 decades, other capsulated serotypes have been recognized increasingly as causing invasive infections. H. influenzae serotype a (Hia) is now a major cause of invasive infection in Indigenous communities of North America, prompting a possible requirement for an Hia conjugate vaccine. H. influenzae serotypes e and f are now more common than serotype b in Europe. Significant year-to-year increases in nontypeable H. influenzae invasive infections have occurred in many regions of the world. Invasive H. influenzae infections are now seen predominantly in patients at the extremes of life and those with underlying comorbidities. This review provides a comprehensive and critical overview of the current global epidemiology of invasive H. influenzae infections in different geographic regions of the world. It discusses those now at risk of invasive Hib disease, describes the emergence of other severe invasive H. influenzae infections, and emphasizes the importance of long-term, comprehensive, clinical and microbiologic surveillance to monitor a vaccine's impact.

Budget impact analysis of introducing a non-reconstituted, hexavalent vaccine for pediatric immunization in the United Kingdom

Objectives: Non-reconstituted, hexavalent vaccines (HV-NRs) can facilitate clinical practice by shortening vaccine preparation and administration time and by reducing the risk of vaccination errors compared to combination vaccines requiring reconstitution. The aim of this study was to determine the budget impact of introducing an HV-NR into the United Kingdom's (UK) pediatric immunization program, which currently uses a hexavalent vaccine requiring reconstitution (HV-R). Methods: Abudget impact model covering a 10-year time horizon was developed. The target population constituted closed UK birth cohorts from 2020 to 2029. Total direct costs from the payer's perspective consisted of four main categories: vaccine acquisition and management, healthcare provider's service provision, (non-)contaminated needle-stick and sharps injury (NSI), and non-NSI vaccination error costs. The net budget impact was calculated by comparing the costs in two different market share scenarios. Results: The use of HV-NR instead of HV-R was estimated to save £9,079,927 over a 10-year time horizon (i.e. £907,993 per year). Assuming all other vaccine criteria are equivalent the budget impact was most sensitive to changes in time spent by the healthcare provider and management costs. Conclusion: Results suggest, introducing an HV-NR into the UK's pediatric immunization program is potentially cost saving for the healthcare system.

Viral-bacterial (co-)occurrence in the upper airways and the risk of childhood pneumonia in resource-limited settings

OBJECTIVE

To examine the association between bacterial-viral co-occurrence in the nasopharynx and the risk of community acquired pneumonia (CAP) in young children living in resource-limited settings.

METHODS

A case-control study was conducted between January and December 2017 in Moshi, Tanzania. Children 2-59 months with CAP and healthy controls were enrolled. RSV and Influenza A/B were detected with a standardized polymerase chain reaction (PCR) method, and a simplified real-time quantitative PCR method, without sample pre-processing, was developed to detect bacterial pathogens in nasopharyngeal samples.

RESULTS

A total of 109 CAP patients and 324 healthy controls were enrolled. Co-detection of H. influenzae and S. pneumoniae in nasopharyngeal swabs was linked with higher odds of CAP (aOR=3.2, 95% CI=1.1-9.5). The majority of the H. influenzae isolated in cases and controls (95.8%) were non-typeable. Of the viruses examined, respiratory syncytial virus (RSV) was most common (n = 31, 7.2%) in cases and controls. Children with RSV had 8.4 times higher odds to develop pneumonia than healthy children (aOR=8.4, 95%CI= 3.2 - 22.1).

CONCLUSIONS

Co-occurence of H. influenzae and S. pneumoniae in the nasopharynx was strongly associated with CAP. The high prevalence of non-typeable H. influenzae might be a sign of replacement as a consequence of Haemophilus influenzae type b vaccination.

Delay in booster schedule as a control parameter in vaccination dynamics

The use of multiple vaccine doses has proven to be essential in providing high levels of protection against a number of vaccine-preventable diseases at the individual level. However, the effectiveness of vaccination at the population level depends on several key factors, including the dose-dependent protection efficacy of vaccine, coverage of primary and booster doses, and in particular, the timing of a booster dose. For vaccines that provide transient protection, the optimal scheduling of a booster dose remains an important component of immunization programs and could significantly affect the long-term disease dynamics. In this study, we developed a vaccination model as a system of delay differential equations to investigate the effect of booster schedule using a control parameter represented by a fixed time-delay. By exploring the stability analysis of the model based on its reproduction number, we show the disease persistence in scenarios where the booster dose is sub-optimally scheduled. The findings indicate that, depending on the protection efficacy of primary vaccine series and the coverage of booster vaccination, the time-delay in a booster schedule can be a determining factor in disease persistence or elimination. We present model results with simulations for a vaccine-preventable bacterial disease, Heamophilus influenzae serotype b, using parameter estimates from the previous literature. Our study highlights the importance of timelines for multiple-dose vaccination in order to enhance the population-wide benefits of herd immunity.

Coverage of Haemophilus influenzae Type b Conjugate Vaccine for Children in Mainland China: Systematic Review and Meta-analysis

BACKGROUND

Use of Haemophilus influenzae type b conjugate vaccine is effective in reducing the disease burden, but its coverage in China is unclear. The aim of this meta-analysis is to assess the coverage of Hib conjugate vaccines in children in Mainland China.

METHODS

We systematically searched Pubmed, Web of Science, Medline, CNKI and Wanfang to identify studies assessing the coverage of Hib vaccine in Chinese children. Random-effects models were used to obtain pooled estimates for Hib vaccine coverage and analyzed heterogeneity with meta-regression and subgroup analyses.

RESULTS

Thirty-three studies that included 7,227,480 subjects in 12 provinces met our inclusion criteria. The pooled overall coverage of Hib conjugate vaccine was 54.9% [95% confidence interval (CI): 52.9-57.0]. The pooled coverage for the nonlocal population (54.3%; 95% CI: 52.4-56.3) was lower than that for the local residents (62.0%; 95% CI: 58.4-65.6). The region-pooled coverage was higher in the east of China (59.7%; 95% CI: 57.3-62.1) than in the central and west parts of the country (48.5%; 95% CI: 40.6-56.4). Overall, 26.7% (95% CI: 20.1-33.2) had 1 dose only, 14.8% (95% CI: 10.0-19.6%) had 2 doses, 13.5% (95% CI: 9.1-17.8) had 3 doses and 14.3% (95% CI: 9.7-18.9) had 4 doses.

CONCLUSIONS

We found a low coverage of Hib conjugate vaccine, particularly for the nonlocal children and those living in the central and west parts of China. Including Hib vaccine into the national immunization program is recommended to reduce disparities in vaccination coverage.

Utilization pattern of Haemophilus influenza type b vaccine in eight provinces of China

OBJECTIVE

In China, Hib vaccine is a private-sector vaccine that is an option for parents to select to give to their children; it must be paid for out-of-pocket because it is not included in the government's Expanded Program on Immunization (EPI). We evaluated utilization patterns of Hib vaccine to provide evidence in support of development of a national Hib vaccination strategy.

METHODS

We obtained lists of children from immunization information systems (IIS) of counties or districts in 8 provinces of China. Using these lists, we selected 10 children at random from each birth cohort from 2008 through 2012. We obtained Hib vaccination dates from official vaccination certificates. The target sample size was 1,000 children.

RESULTS

We were able to obtain records for 978 subjects of the selected subjects; of these, 44.79% had received at least 1 dose of Hib vaccine, and 15.54%, 5.83%, 12.27%, and 11.15% had received one, two, three, and four doses, respectively. Per capita GDP was positively correlated with receipt of at least one dose of Hib vaccine. Among the 438 subjects who received Hib vaccine, 27% received 1 dose after 12 months of age; 15%, 7%, and 23% received one of three other patterns of Hib vaccination recommended by the World Health Organization (WHO) [a 3-dose primary series; 2 primary series doses and 1 booster; or 3 primary series doses and 1 booster]. The other 28% of subjects received patterns of Hib vaccination not recommended by WHO. Considering protection from Hib disease as receipt of a WHO-recommended Hib vaccine schedule, 29% of subjects could be considered protected after 12 months of age, 52% could be considered protected during infancy and beyond, and 19% could be considered to not have been protected adequately, despite being vaccinated.

CONCLUSIONS

Coverage with Hib vaccine was low. There were significant differences between WHO recommendations and actual patterns of use of Hib vaccine, with half of vaccine recipients receiving no protection during infancy and one fifth receiving non-protective Hib vaccination patterns. Inclusion of Hib vaccine into China's EPI system, which provides vaccine at no charge to parents and makes specific vaccination schedule standards, has potential to make more effective use of Hib vaccine.

A bibliometric analysis of systematic reviews on vaccines and immunisation

Introduction

SYSVAC is an online bibliographic database of systematic reviews and systematic review protocols on vaccines and immunisation compiled by the London School of Hygiene & Tropical Medicine and hosted by the World Health Organization (WHO) through their National Immunization Technical Advisory Groups (NITAG) resource centre (www.nitag-resource.org). Here the development of the database and a bibliometric review of its content is presented, describing trends in the publication of policy-relevant systematic reviews on vaccines and immunisation from 2008 to 2016.

Materials and methods

Searches were conducted in seven scientific databases according to a standardized search protocol, initially in 2014 with the most recent update in January 2017. Abstracts and titles were screened according to specific inclusion criteria. All included publications were coded into relevant categories based on a standardized protocol and subsequently analysed to look at trends in time, topic, area of focus, population and geographic location.

Results

After screening for inclusion criteria, 1285 systematic reviews were included in the database. While in 2008 there were only 34 systematic reviews on a vaccine-related topic, this increased to 322 in 2016. The most frequent pathogens/diseases studied were influenza, human papillomavirus and pneumococcus. There were several areas of duplication and overlap.

Discussion

As more systematic reviews are published it becomes increasingly time-consuming for decision-makers to identify relevant information among the ever-increasing volume available. The risk of duplication also increases, particularly given the current lack of coordination of systematic reviews on vaccine-related questions, both in terms of their commissioning and their execution. The SYSVAC database offers an accessible catalogue of vaccine-relevant systematic reviews with, where possible access or a link to the full-text.

Conclusions

SYSVAC provides a freely searchable platform to identify existing vaccine-policy-relevant systematic reviews. Systematic reviews will need to be assessed adequately for each specific question and quality.

Cost-effectiveness of a potential vaccine candidate for Haemophilus influenzae serotype 'a'

The preceding decade has witnessed the emergence of severe community-acquired acute infections caused by Haemophilus influenzae serotype a (Hia), with alarming incidence rates in North America, particularly among indigenous populations. The remarkable success of Hib conjugate vaccine over the past 20 years signify the development of an Hia vaccine candidate as a prevention measure to reduce the incidence of invasive Hia disease. However, quantifications of the long-term epidemiologic and economic impacts of vaccination are needed to inform decision on investment in Hia vaccine development and immunization programs. We sought to evaluate the cost-effectiveness of an Hia vaccine with a similar routine infant immunization schedules currently in practice for Hib in Canada. We developed and parameterized an agent-based simulation model using age-specific incidence rates reported for Nunavut, a Canadian territory with predominantly aboriginal populations. Our results, based on statistical analyses of the incremental cost-effectiveness ratio, show that an Hia conjugate vaccine is highly cost-effective. Sustaining an immunization program with vaccine coverages of 77% for primary series and 93% for booster dose over a 10-year period reduces the incidence of invasive disease by 63.8% on average from 9.97 to 3.61 cases, per 100,000 population. The overall costs of disease management in year 10 are reduced by 53.4% from CDN $1.863 million (95% CI: $1.229-$2.519 M) to CDN $0.868 million (95% CI: $0.627-$1.120 M). The findings suggest an important role for a conjugate vaccine in managing Hia disease as a growing public health threat.

Economic Evaluation and Budget Impact Analysis of Vaccination against Haemophilus influenzae Type b Infection in Thailand

Current study aimed to estimate clinical and economic outcomes of providing the Haemophilus influenzae type b (Hib) vaccination as a national vaccine immunization program in Thailand. A decision tree combined with Markov model was developed to simulate relevant costs and health outcomes covering lifetime horizon in societal and health care payer perspectives. This analysis considered children aged under 5 years old whom preventive vaccine of Hib infection are indicated. Two combined Hib vaccination schedules were considered: three-dose series (3 + 0) and three-dose series plus a booster does (3 + 1) compared with no vaccination. Budget impact analysis was also performed under Thai government perspective. The outcomes were reported as Hib-infected cases averted and incremental cost-effectiveness ratios (ICERs) in 2014 Thai baht (THB) ($) per quality-adjusted life year (QALY) gained. In base-case scenario, the model estimates that 3,960 infected cases, 59 disability cases, and 97 deaths can be prevented by national Hib vaccination program. The ICER for 3 + 0 schedule was THB 1,099 ($34) per QALY gained under societal perspective. The model was sensitive to pneumonia incidence among aged under 5 years old and direct non-medical care cost per episode of Hib pneumonia. Hib vaccination is very cost-effective in the Thai context. The budget impact analysis showed that Thai government needed to invest an additional budget of 110 ($3.4) million to implement Hib vaccination program. Policy makers should consider our findings for adopting this vaccine into national immunization program.

Modelling the effects of booster dose vaccination schedules and recommendations for public health immunization programs: the case of Haemophilus influenzae serotype b

Background

Haemophilus influenzae serotype b (Hib) has yet to be eliminated despite the implementation of routine infant immunization programs. There is no consensus regarding the number of primary vaccine doses and an optimal schedule for the booster dose. We sought to evaluate the effect of a booster dose after receiving the primary series on the long-term disease incidence.

Methods

A stochastic model of Hib transmission dynamics was constructed to compare the long-term impact of a booster vaccination and different booster schedules after receiving the primary series on the incidence of carriage and symptomatic disease. We parameterized the model with available estimates for the efficacy of Hib conjugate vaccine and durations of both vaccine-induced and naturally acquired immunity.

Results

We found that administering a booster dose substantially reduced the population burden of Hib disease compared to the scenario of only receiving the primary series. Comparing the schedules, the incidence of carriage for a 2-year delay (on average) in booster vaccination was comparable or lower than that observed for the scenario of booster dose within 1 year after primary series. The temporal reduction of symptomatic disease was similar in the two booster schedules, suggesting no superiority of one schedule over the other in terms of reducing the incidence of symptomatic disease.

Conclusions

The findings underscore the importance of a booster vaccination for continued decline of Hib incidence. When the primary series provides a high level of protection temporarily, delaying the booster dose (still within the average duration of protection conferred by the primary series) may be beneficial to maintain longer-term protection levels and decelerate the decline of herd immunity in the population.

Electronic supplementary material

The online version of this article (10.1186/s12889-017-4714-9) contains supplementary material, which is available to authorized users.

Antibacterial monoclonal antibodies: the next generation?

There is a clear need for renewed efforts to combat the increasing incidence of antibiotic resistance. While the antibiotic resistance epidemic is due in part to the misuse of antibiotics, even proper empiric antibiotic therapy increases the selective pressure and potential for drug-resistance and spread of resistance mechanisms between bacteria. Antibiotic resistance coupled with the detrimental effects of broad-spectrum antibiotics on the healthy microbiome, have led the field to explore pathogen specific antibacterials such as monoclonal antibodies (mAbs). Medical need along with advances in mAb discovery, engineering, and production have driven significant effort developing mAb-based antibacterials. If successful, they will provide physicians with precision weapons to combat bacterial infections and can help prevent a return to a pre-antibiotic era.

Two or three primary dose regime for Haemophilus influenzae type b conjugate vaccine: meta-analysis of randomized controlled trials

Haemophilus influenzae type b (Hib) is an important cause of meningitis and pneumonia in children. Despite the availability of Hib conjugate vaccine, many countries are still to implement it in their immunization schedule. Before introducing the vaccine in routine immunization programs, it is important to know not only the cumulative efficacy but also the efficacy of each vaccine dose. The primary objective of this review is to find whether two primary dose schedule of Hib vaccine is equally efficacious as the standard three primary dose schedule. A highly sensitive online search was run using the terms 'Haemophilus Vaccines' or 'Haemophilus influenzae type b' and 'conjugate vaccine', and Medline (Ovid), PubMed, Embase, CENTRAL and Scopus were explored for prospective randomized controlled studies. Data were extracted in a predesigned proforma and analyzed using RevMan software. Nine randomized studies were included in the analysis. Pooled vaccine efficacy using a fixed effects model against confirmed invasive Hib disease following the 3, 2 and 1 primary dose schedule were 82% [95% confidence interval (CI) 73-87], 79% (95% CI 54-90) and 65% (95% CI 23-84), respectively, and the overall efficacy was 80% (95% CI 72-85). To conclude, we found that Hib conjugate vaccine is highly efficacious and that the two dose regime is as good as the three dose regime. [The protocol was registered with PROSPERO (CRD42013004490)].

Comparing Haemophilus influenzae type b conjugate vaccine schedules: a systematic review and meta-analysis of vaccine trials

BACKGROUND

The optimal schedule and the need for a booster dose are unclear for Haemophilus influenzae type b (Hib) conjugate vaccines. We systematically reviewed relative effects of Hib vaccine schedules.

METHODS

We searched 21 databases to May 2010 or June 2012 and selected randomized controlled trials or quasi-randomized controlled trials that compared different Hib schedules (3 primary doses with no booster dose [3p+0], 3p+1 and 2p+1) or different intervals in primary schedules and between primary and booster schedules. Outcomes were clinical efficacy, nasopharyngeal carriage and immunological response. Results were combined in random-effects meta-analysis.

RESULTS

Twenty trials from 15 countries were included; 16 used vaccines conjugated to tetanus toxoid (polyribosylribitol phosphate conjugated to tetanus toxoid). No trials assessed clinical or carriage outcomes. Twenty trials examined immunological outcomes and found few relevant differences. Comparing polyribosylribitol phosphate conjugated to tetanus toxoid 3p+0 with 2p+0, there was no difference in seropositivity at the 1.0 μg/mL threshold by 6 months after the last primary dose (combined risk difference -0.02; 95% confidence interval: -0.10, 0.06). Only small differences were seen between schedules starting at different ages, with different intervals between primary doses, or with different intervals between primary and booster doses. Individuals receiving a booster were more likely to be seropositive than those at the same age who did not.

CONCLUSIONS

There is no clear evidence from trials that any 2p+1, 3p+0 or 3p+1 schedule of Hib conjugate vaccine is likely to provide better protection against Hib disease than other schedules. Until more data become available, scheduling is likely to be determined by epidemiological and programmatic considerations in individual settings.