Vaccines for preventing typhoid fever

Non-specific protection against severe COVID-19 associated to typhoid fever and DTP vaccination

Trained immunity (TRAIM) or the enhanced non-specific immune response after primary stimulation by infection or vaccination is a recent but well-recognized concept. To verify its predictions, our objective was to determine the effects of two bacterial vaccines, typhoid fever (TFV) and diphtheria-tetanus-pertussis (DTP) on the infection, hospitalization and death frequencies associated to COVID-19 in a retrospective study on subjects vaccinated or not with TFV and DTP in the 4 years prior to the start of COVID-19 pandemia in the Basque Country (Spain). The studied outcome records were split into two periods according to COVID-19 vaccination, the pre-vaccination (ACV) from March to December 2020 and the post-vaccination (PCV) from September 2021 to June 2022). In total, 13,673 subjects were vaccinated against TFV and 42,997 against DTP. A total of 2,005,084 individual records were studied in the ACV period and 1,436,693 in the PCV period. The proportion of infection, hospitalization and death associated to COVID-19 among controls in ACV was 4.97 %, 7.14 % and 3.54 %, respectively vs. 7.20 %, 2.24 % and 0.10 % among TFV subjects. Regarding DTP, the proportions were 4.97 %, 7.12 % and 3.58 % for controls and 5.79 %, 5.79 % and 0.80 % for vaccinees. In the PCV period, the proportion of infection, hospitalization and death among controls was 21.89 %, 2.62 % and 0.92 %, respectively vs. 31.19 %, 0.76 %, 0.00 % among TFV. For DTP, infection, hospitalization and death proportions were 21.89 %, 2.62 % and 0.92 %, respectively, among controls vs. 32.03 %, 1.85 % and 0.24 % among vaccinated subjects. The corresponding combined ACV and PCV odds ratios (OR) for SARS-CoV2 infection were 1.505 (95%CI 1.455-1.558; p < 0.0001; reduction -41.85 %) and 1.633 (95%CI 1.603-1.662; p < 0.0001; reduction -51.74 %), for TFV and DTP, respectively. Regarding COVID-19 associated hospitalization, the OR were 0.295 (95%CI 0.220-0.396; p = 0.0001; reduction 69.74 %) and 0.667 (95%CI 0.601-0.741; p = 0.0001; reduction 32.44 %), for TFV and DTP, respectively). COVID-19 associated death OR were 0.016 (95%CI 0.002-0.113, p < 0.0001; reduction 98.38 %) and 0.212 (95%CI 0.161-0.280; p = 0.0001; reduction 78.52 %), for TFV and DTP, respectively. We conclude that TRAIM effects by TFV and DTP vaccination in the four years prior to the pandemic SARS-CoV2 were supported by slightly increased infection rates, but strongly reduced COVID-19 associated hospitalization and death rates.

Etiology of Acute Febrile Illnesses in Adults in the Defense Community in French Guiana

In tropical countries, acute febrile illnesses represent a complex clinical problem for general practitioners. We describe the prevalence of different etiologies of acute febrile illnesses occurring among French service members and their families, excluding children, in general practice in French Guiana. From June 2017 to March 2020, patients with a fever ≥37.8°C with a duration of less than 15 days who sought medical care at the army medical centers in Cayenne and Kourou were prospectively enrolled. Based on clinical presentation, blood, urine, nasopharyngeal, and stool samples were collected for diagnostic testing for viruses, bacteria, and parasites (by direct examination, microscopic examination of blood smears, culture, serology, or polymerase chain reaction), and standardized biological tests were systematically performed. Among 175 patients retained for analysis, fever with nonspecific symptoms was predominant (46.9%), with 10 Plasmodium vivax malaria cases, 8 dengue infections, and 6 cases of Q fever. The second most frequent cause of acute febrile illness was upper respiratory tract infections (32.0%) due to influenza virus (n = 18) or human rhinovirus (n = 10). Among the causes of acute febrile illness in French Guiana, clinicians should first consider arboviruses and malaria, as well as Q fever in cases of elevated C-reactive protein with nonspecific symptoms and influenza in cases of signs and symptoms associated with upper respiratory tract infections. Despite an expanded microbiological search, the etiology of 51.4% of acute febrile illnesses remain unknown. Further investigations will be necessary to identify the etiology of acute febrile illnesses, including new pathogens, in French Guiana.

Typhoid Conjugate Vaccine: A Boon for Endemic Regions

Typhoid fever has the highest disease burden in countries in low- and middle-income countries, primarily located in Asia and Sub-Saharan Africa. Previous typhoid vaccines such as the live attenuated typhoid (Ty21a) vaccine and Vi (virulence) capsular polysaccharide vaccine had the limitation that they could not be administered with other standard childhood immunizations and were ineffective in children under two years of age. To address these shortcomings of the previous vaccines, typhoid conjugate vaccines (TCVs) were developed and prequalified by the World Health Organization. Cross-reacting material and tetanus toxoid are widely used as carrier proteins in TCVs. According to various studies, TCV has higher efficacy, has a more extended protection period, and is safe and immunogenic in infants as young as six months. This review article aims to comprehensively appraise the data available on TCVs' efficacy, duration of protection, safety, and immunogenicity in endemic regions.

Climate change affects the spread of typhoid pathogens

Typhoid fever is caused by Salmonella enterica serotype Typhi (Salmonella Typhi). Syndromes in patients vary from asymptomatic carriers to severe or death outcomes, which are frequently reported in African and Southeast Asian countries. It is one of the most common waterborne transmission agents, whose transmission is likely impacted by climate change. Here, we claimed the evidence and consequences of climate-related foodborne and waterborne diseases have increased and provided possible mitigations against Typhoidal Salmonella dissemination.

Vaccines to Control Salmonella in Poultry

This review is focused on describing and analyzing means by which Salmonella enterica serotype strains have been genetically modified with the purpose of developing safe, efficacious vaccines to present Salmonella-induced disease in poultry and to prevent Salmonella colonization of poultry to reduce transmission through the food chain in and on eggs and poultry meat. Emphasis is on use of recently developed means to generate defined deletion mutations to eliminate genetic sequences conferring antimicrobial resistance or residual elements that might lead to genetic instability. Problems associated with prior means to develop vaccines are discussed with presentation of various means by which these problems have been lessened, if not eliminated. Practical considerations are also discussed in hope of facilitating means to move lab-proven successful vaccination procedures and vaccine candidates to the marketplace to benefit the poultry industry.

Typhoid fever

Typhoid fever is an invasive bacterial disease associated with bloodstream infection that causes a high burden of disease in Africa and Asia. Typhoid primarily affects individuals ranging from infants through to young adults. The causative organism, Salmonella enterica subsp. enterica serovar Typhi is transmitted via the faecal-oral route, crossing the intestinal epithelium and disseminating to systemic and intracellular sites, causing an undifferentiated febrile illness. Blood culture remains the practical reference standard for diagnosis of typhoid fever, where culture testing is available, but novel diagnostic modalities are an important priority under investigation. Since 2017, remarkable progress has been made in defining the global burden of both typhoid fever and antimicrobial resistance; in understanding disease pathogenesis and immunological protection through the use of controlled human infection; and in advancing effective vaccination programmes through strategic multipartner collaboration and targeted clinical trials in multiple high-incidence priority settings. This Primer thus offers a timely update of progress and perspective on future priorities for the global scientific community.

Cost-effectiveness analysis of typhoid vaccination in Lao PDR

BACKGROUND

Typhoid vaccination has been shown to be an effective intervention to prevent enteric fever and is under consideration for inclusion in the national immunization program in Lao PDR.

METHODS

A cost-utility analysis was performed using an age-structured static decision tree model to estimate the costs and health outcomes of introducing TCV. Vaccination strategies combined with five delivery approaches in different age groups compared to no vaccination were considered from the societal perspective, using the Gavi price of 1.5 USD per dose. The vaccination program was considered to be cost-effective if the incremental cost-effectiveness ratio was less than a threshold of 1 GDP per capita for Lao PDR, equivalent to USD 2,535 in 2020.

RESULTS

In the model, we estimated 172.2 cases of enteric fever, with 1.3 deaths and a total treatment cost of USD 7,244, based on a birth cohort of 164,662 births without TCV vaccination that was followed over their lifetime. To implement a TCV vaccination program over the lifetime horizon, the estimated cost of the vaccine and administration costs would be between USD 470,934 and USD 919,186. Implementation of the TCV vaccination program would prevent between 14 and 106 cases and 0.1 to 0.8 deaths. None of the vaccination programs appeared to be cost-effective.

CONCLUSIONS

Inclusion of TCV in the national vaccination program in Lao PDR would only be cost-effective if the true typhoid incidence is 25-times higher than our current estimate.

Healthy Drinking Water as a Necessity in Developing Countries Like India: A Narrative review

Water is an indispensable part of human life. This article is an extensive review that focuses on the importance of water to sustain human life, the necessity of healthy, safe drinking water, and the health hazards of drinking untreated and contaminated water. We drink treated water thinking it to be safe without the knowledge that it, too, has harmful effects. Detrimental health effects due to water chlorination are mentioned in this article. The usage of nanoparticles for the treatment of water is an alternative to chlorination, but they are little in use as they are expensive. Transmission of waterborne diseases through drinking water is widespread in a developing country like India. A list of the pathogens contaminating drinking water is present in the review. Pathogens pollute water, and heavy metals and chemicals from industries, pesticides, pharmaceutical compounds, and radioactive waste also taint it. The harmful effects of metal and chemical toxicities on human health are discussed in this review. The government of India has launched several programmes to ensure clean, safe drinking water for all its residents. The study reflects on the treatment given to individuals suffering from waterborne diseases in India. Significant changes in health status in India have been seen recently after the execution of various government programmes to provide safe, healthy drinking water to all its residents.

Travel Medicine

International travel can cause new illness or exacerbate existing conditions. Because primary care providers are frequent sources of health advice to travelers, they should be familiar with destination-specific disease risks, be knowledgeable about travel and routine vaccines, be prepared to prescribe chemoprophylaxis and self-treatment regimens, and be aware of travel medicine resources. Primary care providers should recognize travelers who would benefit from referral to a specialized travel clinic for evaluation. Those requiring yellow fever vaccination, immunocompromised hosts, pregnant persons, persons with multiple comorbid conditions, or travelers with complex itineraries may warrant specialty referral.

Coverage survey of typhoid conjugate vaccine among children aged 6 months to 15 years in an urban slum settlement of Lyari Town Karachi, Pakistan

OBJECTIVE

To estimate the coverage rate of typhoid conjugate vaccine (TCV) among children aged 6 months to 15 years in Lyari Town Karachi, Pakistan.

METHODS

A cross-sectional survey was conducted to estimate the vaccine coverage of Typbar TCV in Lyari Town Karachi utilizing the World Health Organization (WHO) recommended rapid vaccine coverage assessment technique (30 clusters × 7 households). Sampling was powered at town level and multistage cluster sampling was used. Four union councils were randomly selected from a total of 11 and the survey was conducted in those union councils. After consent was obtained, parents of age-eligible children living in the selected union councils were invited to participate in the survey and information was collected on Typbar TCV vaccination status of children aged 6 months to 15 years.

RESULTS

Overall, 2325 children were included in the survey. The mean age of the participants was 7.60 ± 3.84 years. The ratio of males to females was equal in the survey sample; 1163 (50.02%) were male. In the total target population, 82% children were found to be vaccinated; however, the vaccination status could be verified for 80%. The vaccine coverage of TCV was comparable among the four union councils and the overall coverage of TCV vaccine in Lyari Town was found to be 80%. The coverage was significantly lower in younger children, 5% and 17% among children aged 6 months to < 2 years and 2 years to < 5 years respectively and 78% among children aged 5 years to 15 years.

CONCLUSION

The overall immunization coverage rate with TCV was found to be satisfactory. Immunization coverage was comparable among both sexes and the selected union councils but it was relatively low among children in younger age groups.

Remotely Controllable Engineered Bacteria for Targeted Therapy of Pseudomonas aeruginosa Infection

Pseudomonas aeruginosa (P. aeruginosa) infection has become an intractable problem worldwide due to the decreasing efficacy of the mainstay therapy, antibiotic treatment. Hence, exploring new drugs and therapies to address this issue is crucial. Here, we construct a chimeric pyocin (ChPy) to specifically kill P. aeruginosa and engineer a near-infrared (NIR) light-responsive strain to produce and deliver this drug. Our engineered bacterial strain can continuously produce ChPy in the absence of light and release it to kill P. aeruginosa via remotely and precisely controlled bacterial lysis induced by NIR light. We demonstrate that our engineered bacterial strain is effective in P. aeruginosa-infected wound therapy in the mouse model, as it eradicated PAO1 in mouse wounds and shortened the wound healing time. Our work presents a potentially spatiotemporal and noninvasively controlled therapeutic strategy of engineered bacteria for the targeted treatment of P. aeruginosa infections.

Enteric Fever: Diagnostic Challenges and the Importance of Early Intervention

Enteric fever is a systemic infection caused by highly virulent Salmonella enterica serovars: Typhi and Paratyphi. Diagnosis of enteric fever is challenging due to a wide variety of clinical features which overlap with other febrile illnesses. The current diagnostic methods are limited because of the suboptimal sensitivity of conventional tests like blood culture in detecting organisms and the invasive nature of bone marrow culture. It emphasizes the need to develop improved and more reliable diagnostic modalities. The rising rates of multidrug-resistant Salmonella strains call for an accurate understanding of the current management of the disease. Proper public health measures and large-scale immunization programs will help reduce the burden of the disease. A comprehensive surveillance system can help detect the chronic carrier state and is crucial in understanding antibiotic susceptibility patterns. We conducted an all-language literature search on Medline, Cochrane, Embase, and Google Scholar till May 2022. The following search words and medical subject headings (MeSH) were used: "enteric fever," "Salmonella Typhi," "multidrug-resistant Salmonella," chronic carrier state," "Salmonella detection, "and "typhoid vaccine." We reviewed the literature on clinical features, pathophysiology, new diagnostic tests, and interventions to prevent the disease. This article explores enteric fever and its various clinical features and addresses the emerging threat of multidrug resistance. It focuses on novel methods for diagnosis and prevention strategies, including vaccines and the use of surveillance systems employed across different parts of the world.

Profiling of Humoral Immune Response in Typhoid Patients against Differentially Extracted Whole Cell Bacterial Protein Derived from S. typhi and S. spp

Typhoid fever is a multiorgan infectious disease caused by Salmonella typhi. It is transmitted through fecal oral route and can be fatal without proper treatment. Therefore, early diagnosis of typhoid fever is crucial. In the previous study, we have developed TYPHOIDYNE EIA, which showed excellent synergy between the genus conserved and species-specific antigens in the serodiagnosis of typhoid fever. TYPHOIDYNE EIA can effectively detect and differentiate typhoid patients, typhoid vaccinated subjects, healthy subjects, and subjects with other febrile illnesses. Following the successful development of TYPHOIDYNE EIA, in this report, we further characterize the antigenic components of differentially extracted S. typhi and S. spp recognized by IgM, IgG, and IgA antibody isotypes in typhoid patients and possible typhoid carrier by the western blot (WB) assay. The WB characterization revealed a dynamic pattern of recognition, with significant variations in the number of antigenic bands observed between the differentially extracted arrays of antigens. The reactivity of patient’s sera was divided into 3 regions, with region 1 (≥55 kDa) showing the strongest reactivity followed by region 2 (54 kDa–34 kDa) and region 3 (<34 kDa). Overall, the good synergy expressed in these bands suggests the potential role of these proteins in differentiating typhoid patients with possible typhoid carrier. The antigenic bands highlighted in this study are also identified as prospective biomarkers for diagnostic use and vaccine development.

Vi polysaccharide and conjugated vaccines afford similar early, IgM or IgG-independent control of infection but boosting with conjugated Vi vaccines sustains the efficacy of immune responses

Introduction

Vaccination with Vi capsular polysaccharide (Vi-PS) or protein-Vi typhoid conjugate vaccine (TCV) can protect adults against Salmonella Typhi infections. TCVs offer better protection than Vi-PS in infants and may offer better protection in adults. Potential reasons for why TCV may be superior in adults are not fully understood.

Methods and results

Here, we immunized wild-type (WT) mice and mice deficient in IgG or IgM with Vi-PS or TCVs (Vi conjugated to tetanus toxoid or CRM197) for up to seven months, with and without subsequent challenge with Vi-expressing Salmonella Typhimurium. Unexpectedly, IgM or IgG alone were similarly able to reduce bacterial burdens in tissues, and this was observed in response to conjugated or unconjugated Vi vaccines and was independent of antibody being of high affinity. Only in the longer-term after immunization (>5 months) were differences observed in tissue bacterial burdens of mice immunized with Vi-PS or TCV. These differences related to the maintenance of antibody responses at higher levels in mice boosted with TCV, with the rate of fall in IgG titres induced to Vi-PS being greater than for TCV.

Discussion

Therefore, Vi-specific IgM or IgG are independently capable of protecting from infection and any superior protection from vaccination with TCV in adults may relate to responses being able to persist better rather than from differences in the antibody isotypes induced. These findings suggest that enhancing our understanding of how responses to vaccines are maintained may inform on how to maximize protection afforded by conjugate vaccines against encapsulated pathogens such as S. Typhi.

A Phase II/III, Multicenter, Observer-blinded, Randomized, Non-inferiority and Safety, study of typhoid conjugate vaccine (EuTCV) compared to Typbar-TCV® in healthy 6 Months-45 years aged participants

The typhoid conjugate vaccine (TCV) ensures a long-lasting protective immune response, requires fewer doses and is fit for children under 2 years of age. From Phase I study, EuTCV displayed considerable immunogenicity and reliable safety, thus endorsing further examination in Phase II/III trials. Therefore, a clinical Phase II/III study (NCT04830371) was conducted to evaluate its efficacy in healthy Filipino participants aged 6 months to 45 years through administration of the test vaccine (Arm A, B, and C) or comparator vaccine Typbar-TCV® (Arm D). Sera samples were collected pre-vaccination (Visit 1) and post-vaccination (Visit 4, Day 28) to assess the immunogenicity of EuTCV and Typbar-TCV®. During the study, participants were regularly monitored through scheduled visits to the clinic to report any adverse events associated with the vaccine. For vaccine safety, the proportion of solicited and unsolicited Treatment-Emergent Adverse Events was all comparable between EuTCV and Typbar-TCV® groups. A single dose of EuTCV produced seroconversion in 99.4% of treated participants, with seroconversion rates non-inferior to that of Typbar-TCV®. Batch-to-batch consistency was concluded based on the 90% Confidence Interval of the geometric mean ratio (EuTCV Arm A, B, and C) at Week 4, lying within the equivalence margin of 0.5 to 2.0 for all batches. Results from this Phase II/III clinical trial of EuTCV in healthy volunteers show comparable safety and considerable immunogenicity, compared to Typbar-TCV®, meeting the objectives of this pivotal study. ClinicalTrials.gov registration number: NCT04830371.

Effect of novel therapeutic medicine swertiamarin from Enicostema axillare in zebrafish infected with Salmonella typhi

Herbal treatments have been practiced by humans over centuries and therefore possess time-proven safety. However, it is crucial to evaluate the toxic effects of herbal medicine to confirm their safety, particularly when developing therapeutic drugs. Use of laboratory animals such as mice, rat, and rabbits was considered as gold standard in herbal toxicity assessments. However, in the last few decades, the ethical consideration of using higher vertebrates for toxicity testing has become more controversial. As a possible alternative model involving lower vertebrates such as zebra fish were introduced. Hence in the present study, swertiamain compound isolated from E. axillare was assessed for it antimicrobial activity in zebra fish larvae againt S. typhi. The cumulative mortality rate and bacterial localization in zebra fish larvae were studied. Biochemical markers assays were performed to find the preventive role of the compound during the typhoid infection. The results showed that zebra fish can be successfully used as a model to study typhoid infection and the anti-bacterial compound swertiamarin used in this study clears the bacterial load and pathogenic symptoms to a great extent.

Implementation of an outbreak response vaccination campaign with typhoid conjugate vaccine – Harare, Zimbabwe, 2019

Introduction

Typhoid fever is a public-health problem in Harare, the capital city of Zimbabwe, with seasonal outbreaks occurring annually since 2010. In 2019, the Ministry of Health and Child Care (MOHCC) organized the first typhoid conjugate vaccination campaign in Africa in response to a recurring typhoid outbreak in a large urban setting.

Method

As part of a larger public health response to a typhoid fever outbreak in Harare, Gavi approved in September 2018 a MOHCC request for 340,000 doses of recently prequalified Typbar-TCV to implement a mass vaccination campaign. To select areas for the campaign, typhoid fever surveillance data from January 2016 until June 2018 was reviewed. We collected and analyzed information from the MOHCC and its partners to describe the vaccination campaign planning, implementation, feasibility, administrative coverage and financial costs.

Results

The campaign was conducted in nine high-density suburbs of Harare over eight days in February–March 2019 and targeted all children aged 6 months–15 years; however, the target age range was extended up to 45 years in one suburb due to the past high attack rate among adults. A total of 318,698 people were vaccinated, resulting in overall administrative coverage of 85.4 percent. More than 750 community volunteers and personnel from the MOHCC and the Ministry of Education were trained and involved in social mobilization and vaccination activities. The MOHCC used a combination of vaccination strategies (i.e., fixed and mobile immunization sites, a creche and school-based strategy, and door-to-door activities). Financial costs were estimated at US$ 2.39 per dose, including the vaccine and vaccination supplies (US$ 0.79 operational costs per dose excluding vaccine and vaccination supplies).

Conclusion

A mass targeted campaign in densely populated urban areas in Harare, using the recently prequalified typhoid conjugate vaccine, was feasible and achieved a high overall coverage in a short period of time.

A multicenter, single-blind, randomized, phase-2/3 study to evaluate immunogenicity and safety of a single intramuscular dose of biological E's Vi-capsular polysaccharide-CRM197 conjugate typhoid vaccine (TyphiBEVTM) in healthy infants, children, and adults in comparison with a licensed comparator

The current scenario of typhoid fever warrants early prevention with typhoid conjugate vaccines in susceptible populations to provide lifelong protection. We conducted a multicenter, single-blind, randomized, Phase 2/3 study to assess the immunogenicity and safety of Biological E’s Typhoid Vi-CRM₁₉₇ conjugate vaccine (TyphiBEV^TM) compared to Vi-TT conjugate vaccine manufactured by Bharat Biotech International Limited (Typbar-TCV; licensed comparator) in healthy infants, children, and adults from India. The study’s primary objective was to assess the non-inferiority of TyphiBEV^TM in terms of the difference in the proportion of subjects seroconverted with a seroconversion threshold value of ≥2.0 µg/mL against Typbar-TCV. A total of 622 healthy subjects (311 each in both vaccine groups) were randomized and received the single dose of the study vaccine. The TyphiBEV^TM group demonstrated noninferiority compared to the Typbar-TCV group at Day 42. The lower 2-sided 95% confidence interval limit of the group difference was −.34%, which met the non-inferiority criteria of ≥10.0%. The geometric mean concentration (24.79 µg/mL vs. 26.58 µg/mL) and proportion of subjects who achieved ≥4-fold increase in antiVi IgG antibody concentrations (96.95% vs. 97.64%) at Day 42 were comparable between the TyphiBEV^TM and Typbar-TCV vaccine groups. No apparent difference was observed in the safety profile between both vaccine groups. All adverse events reported were mild or moderate in intensity in all age subsets. This data demonstrates that TyphiBEV^TM is non-inferior to TypbarTCV in terms of immunogenicity, and the overall safety and reactogenicity in healthy infants, children, and adults studied from India was comparable.

Chitosan-Based Nanomaterial as Immune Adjuvant and Delivery Carrier for Vaccines

With the support of modern biotechnology, vaccine technology continues to iterate. The safety and efficacy of vaccines are some of the most important areas of development in the field. As a natural substance, chitosan is widely used in numerous fields-such as immune stimulation, drug delivery, wound healing, and antibacterial procedures-due to its good biocompatibility, low toxicity, biodegradability, and adhesion. Chitosan-based nanoparticles (NPs) have attracted extensive attention with respect to vaccine adjuvants and delivery systems due to their excellent properties, which can effectively enhance immune responses. Here, we list the classifications and mechanisms of action of vaccine adjuvants. At the same time, the preparation methods of chitosan, its NPs, and their mechanism of action in the delivery system are introduced. The extensive applications of chitosan and its NPs in protein vaccines and nucleic acid vaccines are also introduced. This paper reviewed the latest research progress of chitosan-based NPs in vaccine adjuvant and drug delivery systems.

A scoping review of active, participant-centred, digital adverse events following immunization (AEFI) surveillance: A Canadian immunization research network study

BACKGROUND

Post-licensure adverse events following immunization (AEFI) surveillance is conducted to monitor vaccine safety, such as identifying batch/brand issues and rare reactions, which consequently improves community confidence. The integration of technology has been proposed to improve AEFI surveillance, however, there is an absence of description regarding which digital solutions are successfully being used and their unique characteristics.

OBJECTIVES

The objectives of this scoping review were to 1) map the research landscape on digital systems used for active, participant-centred, AEFI surveillance and 2) describe their core components.

METHODS

We conducted a scoping review informed by the PRISMA Extension for Scoping Reviews (PRSIMA-ScR) guideline. OVID-Medline, Embase Classic + Embase, and Medrxiv were searched by a medical librarian from January 1, 2000 to January 28th, 2021. Two independent reviewers determined which studies met inclusion based on pre-specified eligibility criteria. Data extraction was conducted using pre-made tables with specific variables by one investigator and verified by a second.

RESULTS

Twenty-seven publications met inclusion, the majority of which came from Australia (n = 15) and Canada (n = 6). The most studied active, participant-centred, digital AEFI surveillance systems were SmartVax (n = 8) (Australia), Vaxtracker (n = 7) (Australia), and Canadian National Vaccine Safety (CANVAS) Network (Canada) (n = 6). The two most common methods of communicating with vaccinees reported were short-message-service (SMS) (n = 15) and e-mail (n = 14), with online questionnaires being the primary method of data collection (n = 20).

CONCLUSION

Active, participant-centred, digital AEFI surveillance is an area actively being researched as depicted by the literature landscape mapped by this scoping reviewWe hypothesize that the AEFI surveillance approach herein described could become a primary method of collecting self-reported subjective symptoms and reactogenicity from vaccinees, complementing existing systems. Future evaluation of identified digital solutions is necessary to bring about improvements to current vaccine surveillance systems to meet contemporary and future public health needs.

A typhoid fever protein capsular matrix vaccine candidate formulated with Advax-CpG adjuvant induces a robust and durable anti-typhoid Vi polysaccharide antibody response in mice, rabbits and nonhuman primates

Typhax is an investigational typhoid fever vaccine candidate that is comprised of Vi polysaccharide from Salmonella enterica serovar typhi (S. Typhi) non-covalently entrapped in a glutaraldehyde catalyzed, cross-linked α-poly-L-lysine and CRM₁₉₇ protein matrix. A previous Phase 1 trial of an aluminum phosphate adjuvanted Typhax formulation showed it induced Vi IgG after a single dose but that subsequent doses failed to further boost Vi IgG levels. The current study asked whether Advax-CpG adjuvant might instead be able to overcome polysaccharide-induced immune inhibition and improve Typhax immunogenicity. Advax-CpG adjuvanted Typhax elicited high and sustained Vi IgG responses in mice, rabbits and non-human primates (NHP) with levels being boosted by repeated immunization. High Vi antibody responses were lost in CD4 + T cell depleted mice confirming that despite the lack of conjugation of the polysaccharide to the carrier protein, Typhax nevertheless acts in a T cell dependent manner, explaining its ability to induce long-term B cell memory responses to Vi capable of being boosted. In NHP, Advax-CpG adjuvanted Typhax induced up to 100-fold higher Vi IgG levels than the commercial Typhim Vi polysaccharide vaccine. Typhax induced high and sustained serum bactericidal activity against S. Typhi and stimulated robust Vi IgG responses even in animals previously primed with a pure polysaccharide vaccine. Hence Advax-CpG adjuvanted Typhax vaccine is a highly promising candidate to provide robust and durable protection against typhoid fever.

Fever in the Returning Traveler

BACKGROUND

It is predicted that approximately two billion tourist trips to foreign countries will be taken worldwide each year by 2030. Germany has long been among the most active countries in tourism. The frequency of illness among persons returning from developing and newly industrialized countries is 43-79%. The appropriate diagnosis of fever in returning travelers is a clinically important matter, as it can be a sign of a life-threatening illness.

METHODS

This review is based on publications (2001-2022) retrieved by a selective search in PubMed for studies on the epidemiology, diagnosis, and treatment of febrile illnesses in returning travelers, or on specific tropical diseases.

RESULTS

Diarrhea, fever, and skin changes are the most common manifestations of disease after travel to tropical and sub - tropical areas. The diagnostic evaluation should be performed in a series of steps, beginning with a precise travel history and the identification of specific risk factors. Among travelers returning from sub-Saharan Africa, Plasmodium falciparum malaria is the most common cause of fever on presentation to centers for infectious diseases and tropical medicine, affecting approximately 50 per 1000 travelers. Among persons returning from travel to Southeast Asia, dengue fever is the most common infectious disease, affecting 50-160 per 1000 travelers. Further potentially dangerous diseases include chikungunya and zika fever, typhoid and paratyphoid fever, amoebic liver abscess, visceral leishmaniasis (kala-azar), leptospirosis, and, very rarely, imported cases of viral hemorrhagic fever. COVID-19 and influenza are important differential diagnoses.

CONCLUSION

The differential diagnosis can be narrowed by thorough history-taking with particular attention to the patient's travel route, combined with a good knowledge of the geographic spread and incubation times of the main tropical diseases. Algorithms help clinicians to focus the diagnostic work-up and select the appropriate further laboratory tests and diagnostic procedures.

Typhoid toxin sorting and exocytic transport from Salmonella Typhi-infected cells

Typhoid toxin is an essential virulence factor for Salmonella Typhi, the cause of typhoid fever in humans. This toxin has an unusual biology in that it is produced by Salmonella Typhi only when located within host cells. Once synthesized, the toxin is secreted to the lumen of the Salmonella-containing vacuole from where it is transported to the extracellular space by vesicle carrier intermediates. Here, we report the identification of the typhoid toxin sorting receptor and components of the cellular machinery that packages the toxin into vesicle carriers, and exports it to the extracellular space. We found that the cation-independent mannose-6-phosphate receptor serves as typhoid toxin sorting receptor and that the coat protein COPII and the GTPase Sar1 mediate its packaging into vesicle carriers. Formation of the typhoid toxin carriers requires the specific environment of the Salmonella Typhi-containing vacuole, which is determined by the activities of specific effectors of its type III protein secretion systems. We also found that Rab11B and its interacting protein Rip11 control the intracellular transport of the typhoid toxin carriers, and the SNARE proteins VAMP7, SNAP23, and Syntaxin 4 their fusion to the plasma membrane. Typhoid toxin's cooption of specific cellular machinery for its transport to the extracellular space illustrates the remarkable adaptation of an exotoxin to exert its function in the context of an intracellular pathogen.

Natural SARS-CoV-2 Infection Affects Neutralizing Activity in Saliva of Vaccinees

Background

SARS-CoV-2 transmission mainly occurs through exposure of the upper airway mucosa to infected secretions such as saliva, which are excreted by an infected person. Thus, oral mucosal immunity plays a central role in the prevention of and early defense against SARS-CoV-2 infection. Although virus-specific antibody response has been extensively investigated in blood samples of SARS-CoV-2-infected patients and vaccinees, local humoral immunity in the oral cavity and its relationship to systemic antibody levels needs to be further addressed.

Material and Methods

We fine-tuned a virus neutralization assay (vNTA) to measure the neutralizing activity (NA) of plasma and saliva samples from 20 SARS-CoV-2-infected (SI), 40 SARS-CoV-2-vaccinated (SV), and 28 SARS-CoV-2-vaccinated subjects with a history of infection (SIV) using the “wild type” SARS-CoV-2 lineage B.1 (EU) and the Delta (B.1.617.2) strains. To validate the vNTA results, the presence of neutralizing antibodies (NAbs) to the spike receptor binding domain (RBD) was evaluated with an ELISA assay.

Results

NA to SARS-CoV-2 lineage B.1 (EU) was present in plasma samples from all the tested subjects, with higher titers in SIV compared to both SI and SV. Conversely, NA was detected in saliva samples from 10.3% SV, 45% SI, and 92.6% SIV, with significantly lower titers in SV compared to both SI and SIV. The detection of NAbs in saliva reflected its reduced NA in SV.

Discussion

The difference in NA of plasma vs. saliva was confirmed in a vNTA where the SARS-CoV-2 B.1 and Delta strains were tested head-to-head, which also revealed a reduced NA of both specimens compared to the B.1 variant.

Conclusions

The administration of SARS-CoV-2 vaccines was associated with limited virus NA in the oral cavity, as measured in saliva and in comparison to plasma. This difference was more evident in vaccinees without a history of SARS-CoV-2 infection, possibly highlighting the importance of local exposure at the site of virus acquisition to effectively prevent the infection and block its spread. Nevertheless, the presence of immune escape mutations as possibly represented by the SARS-CoV-2 Delta variant negatively affects both local and systemic efficacy of NA associated with vaccination.

Population-Based Incidence of Guillain-Barré Syndrome During Mass Immunization With Viral Vaccines: A Pooled Analysis

Misunderstanding temporal coincidence of adverse events during mass vaccination and invalid assessment of possible safety concerns have negative effects on immunization programs, leading to low immunization coverage. We conducted this systematic review and meta-analysis to identify the incidence rates of GBS that are temporally associated with viral vaccine administration but might not be attributable to the vaccines. By literature search in Embase and PubMed, we included 48 publications and 2,110,441,600 participants. The pooled incidence rate of GBS was 3.09 per million persons (95% confidence interval [CI]: 2.67 to 3.51) within six weeks of vaccination, equally 2.47 per 100,000 person-year (95%CI: 2.14 to 2.81). Subgroup analyses illustrated that the pooled rates were 2.77 per million persons (95%CI: 2.47 to 3.07) for individuals who received the influenza vaccine and 2.44 per million persons (95%CI: 0.97 to 3.91) for human papillomavirus (HPV) vaccines, respectively. Our findings evidence the GBS-associated safety of virus vaccines. We present a reference for the evaluation of post-vaccination GBS rates in mass immunization campaigns, including the SARS-CoV-2 vaccine.

Investigating the Efficiency of Recombinant FliC-Loaded Bacillus subtilis Spores in Mice Immunization against Salmonella enterica Serovar Typhi

Background:

Bacterial spores are among the most efficient vaccine delivery vehicles. Because of their safety and efficacy, Bacillus subtilis spores are increasingly used in this regard. The negatively charged surfaces of the spores allow antigens to be adsorbed onto these structures. In this study, a candidate vaccine against Salmonella enterica serovar Typhi was adsorbed onto B. subtilis spores and the immunogenicity of the formulation was investigated in BALB/c mice.

Methods:

This work was performed during 2018–2019 in Islamic Azad University of Lahijan. FliC protein was recombinantly expressed in E. coli BL21 (DE3) cells and purified by affinity chromatography. On the other hand, B. subtilis strain PY79 (ATCC1609) was cultured in DSM medium and after the sporulation, FliC protein was adsorbed onto the spores in three different pH values (4, 7 and 10) and the adsorption was verified using dot-blot assay. FliC-adsorbed spores were then administered to BALB/c mice through the subcutaneous route. Mice immunization was evaluated by serum IgG assessment and challenge study.

Results:

FliC protein was successfully expressed and purified. Sporulation was controlled by phase-contrast microscopy. Serum IgG assay showed significant stimulation of the mice’s humoral immune system. Immunized mice were able to resist bacterial infection.

Conclusion:

The results showed the efficiency of spores as natural adjuvants for the stimulation of mice immune system. The formulation can be exploited for the delivery of recombinant vaccines against bacterial pathogens.

Effectiveness of typhoid conjugate vaccine against culture-confirmed Salmonella enterica serotype Typhi in an extensively drug-resistant outbreak setting of Hyderabad, Pakistan: a cohort study

BACKGROUND

Salmonella enterica serotype Typhi (S Typhi) is a major public health problem in low-income and middle-income countries. We aimed to investigate the effectiveness and impact of the typhoid conjugate vaccine Typbar-TCV against S Typhi among children in an outbreak setting of extensively drug-resistant (XDR) S Typhi in Pakistan.

METHODS

This cohort study was done from Feb 21, 2018, to Dec 31, 2019. A census survey of all households located in the Qasimabad and Latifabad subdistricts of Hyderabad, Pakistan, was done at baseline, and 174 005 households were registered in the census. The Typbar-TCV immunisation campaign was initiated at temporary vaccination centres and 207 000 children aged 6 months to 10 years were vaccinated from Feb 21, 2018, to Dec 31, 2018. Social mobilisers informed parents about the vaccination process. Vaccination records were maintained electronically and linked with the household census surveys. Active surveillance for suspected and blood-culture-confirmed S Typhi was established in hospitals, clinics, and laboratories to assess the following outcomes: cases of suspected typhoid fever, culture-confirmed S Typhi, and antimicrobial resistance. An age-stratified cohort of 1100 vaccinated children was randomly selected from the vaccination registry, tested for Vi-IgG antibodies (data not reported), and followed up fortnightly (via telephone calls or household visits) until Dec 31, 2019, for ascertainment of outcomes during the study period. 20 847 vaccinated and unvaccinated children were randomly selected from the census registry as a quality control cohort and followed up from Oct 1 to Dec 31, 2019, for ascertainment of outcomes. Vaccine effectiveness against suspected, culture-confirmed, and XDR S Typhi was calculated.

FINDINGS

23 407 children from the census registry and surveillance system were included in the vaccine effectiveness analysis. 13 436 (57·4%) children were vaccinated, 12 214 (52·2%) were male, and 10 168 (43·4%) were aged 6-59 months. 5378 (23·0%) of 23 407 children had suspected S Typhi, among whom 775 (14·4%) had culture-confirmed S Typhi and 361 (68·6%) of 526 had XDR S Typhi. Vaccine effectiveness was 55% (95% CI 52-57) against suspected S Typhi (regardless of culture confirmation), 95% (93-96) against culture-confirmed S Typhi, and 97% (95-98) against XDR S Typhi.

INTERPRETATION

Typbar-TCV is effective in protecting children against S Typhi infection in an outbreak setting, and was able, with moderate deployment, to curtail a major XDR S Typhi outbreak in a densely populated setting. The vaccine shows efficacy against S Typhi irrespective of antimicrobial resistance.

FUNDING

Bill & Melinda Gates Foundation.

Evolving pharmacovigilance requirements with novel vaccines and vaccine components

This paper explores the pipeline of new and upcoming vaccines as it relates to monitoring their safety. Compared with most currently available vaccines, that are constituted of live attenuated organisms or inactive products, future vaccines will also be based on new technologies. Several products that include such technologies are either already licensed or at an advanced stage of clinical development. Those include viral vectors, genetically attenuated live organisms, nucleic acid vaccines, novel adjuvants, increased number of antigens present in a single vaccine, novel mode of vaccine administration and thermostabilisation. The Global Advisory Committee on Vaccine Safety (GACVS) monitors novel vaccines, from the time they become available for large scale use. GACVS maintains their safety profile as evidence emerges from post-licensure surveillance and observational studies. Vaccines and vaccine formulations produced with novel technologies will have different safety profiles that will require adapting pharmacovigilance approaches. For example, GACVS now considers viral vector templates developed on the model proposed by Brighton Collaboration. The characteristics of those novel products will also have implications for the risk management plans (RMPs). Questions related to the duration of active monitoring for genetic material, presence of adventitious agents more easily detected with enhanced biological screening, or physiological mechanisms of novel adjuvants are all considerations that will belong to the preparation of RMPs. In addition to assessing those novel products and advising experts, GACVS will also consider how to more broadly communicate about risk assessment, so vaccine users can also benefit from the committee’s advice.

Safety and immunogenicity of Vi-typhoid conjugate vaccine co-administration with routine 9-month vaccination in Burkina Faso: A randomized controlled phase 2 trial

•

This is the first study on the co-administration of typhoid conjugate vaccine (TCV) in West Africa.

•

Co-administration of TCV with routine vaccines in a typhoid-endemic country was successful.

•

TCV was safely co-administered at nine months with yellow fever and measles-rubella vaccines.

•

Single-dose TCV was immunogenic in 9-month-old children.

•

There was no safety signal related to TCV vaccination or co-administration.

Objectives

In 2017, the World Health Organisation (WHO) pre-qualified a single-dose typhoid conjugate vaccine (TCV) and identified TCV co-administration studies as a research priority. Accordingly, we tested co-administration of Typbar TCV® (Bharat Biotech International) with measles-rubella (MR) and yellow fever (YF) vaccines.

Methods

We conducted a randomized, double-blind, and controlled, phase 2 trial in Ouagadougou, Burkina Faso. Healthy children aged 9–11 months were randomized 1:1 to receive TCV (Group 1) or control vaccine (inactivated polio vaccine (IPV), Group 2). Vaccines were administered intramuscularly with routine MR and YF vaccines. Safety was assessed by (1) local and systemic reactions on days 0, 3, and 7; (2) unsolicited adverse events within 28 days; and (3) serious adverse events (SAEs) within six months after immunization.

Results

We enrolled, randomized, and vaccinated 100 eligible children (49 Group 1 and 51 Group 2). Safety outcomes occurred with similar frequency in both groups: local/solicited reactions (Group 1: 1/49, Group 2: 3/50), systemic/solicited reactions (Group 1: 4/49, Group 2: 9/50), unsolicited adverse events (Group 1: 26/49, Group 2: 33/51), and SAEs (Group 1: 2/49, Group 2: 3/51). TCV conferred robust immunogenicity without interference with MR or YF vaccines.

Conclusion

TCV can be safely co-administered with MR and YF vaccines to children at the 9-month vaccination visit.

Robust immunity induced by multi-epitope DnaK peptides, potential vaccine candidates against Salmonella: An in vitro study

Enteric fever is a common yet serious issue, most troublesome in underdeveloped and developing nations affecting all age group primarily children. Pitfalls of existing vaccines along with rapidly rising Multi-Drug-Resistant Salmonella strains necessitate the need for the development of new vaccine candidates having potential to provide complete protection. Several vaccine strategies are being pursued to stimulate protective immunity against typhoid, including conjugate vaccines for the elicitation of cellular and humoral responses as both arms of immunity are essential for complete protection. Bacterial HSPs are highly immunogenic to produce humoral and cellular immune responses. In this study, we are reporting in vitro immunostimulatory activity of immunodominant multi-epitope protective antigenic DnaK peptides identified earlier by immunoinformatics approach. Remarkable increase in antibody titer, lymphocyte proliferation, cytokines and NO level with individual /mixture of DnaK peptides as compared to control demonstrate immunogenic potential of these peptides that effectively augments both humoral and cellular immune responses. None of the peptides cause any hemolysis in human RBCs. Overall; our findings strongly elucidate the immune-stimulatory potential of DnaK peptides to be explored as potent vaccine candidates against multiple pathogens.

Typhoid and paratyphoid fever: a clinical seminar

Rationale for review: Enteric fever (EF) caused by Salmonella enterica subspecies enterica serovar Typhi (Salmonella Typhi) and S. Paratyphi (Salmonella Paratyphi) remains an important cause of infectious morbidity and mortality in many low-income countries and, therefore, still poses a major infectious risk for travellers to endemic countries. Main findings: Although the global burden of EF has decreased over the past two decades, prevalence of EF remains high in Asia and Africa, with the highest prevalence reported from the Indian subcontinent. These statistics are mirrored by data on travel-related EF. Widespread and increasing antimicrobial resistance has narrowed treatment options for travel-related EF. Ceftriaxone- and azithromycin-based therapies are commonly used, even with the emergence of extremely drug-resistant typhoid in Pakistan. Preventive measures among locals and travellers include provision of safe food and water and vaccination. Food and water precautions offer limited protection, and the efficacy of Salmonella Typhi vaccines is only moderate signifying the need for travellers to be extra cautious. Recommendations: Improvement in the diagnosis of typhoid with high degree of clinical suspicion, better diagnostic assays, early and accurate detection of resistance, therapy with appropriate drugs, improvements in hygiene and sanitation with provision of safe drinking water in endemic areas and vaccination among travellers as well as in the endemic population are keys to controlling typhoid. While typhoid vaccines are recommended for travellers to high-risk areas, moderate efficacy and inability to protect against Salmonella Paratyphi are limitations to bear in mind. Improved Salmonella Typhi vaccines and vaccines against Salmonella Paratyphi A are required.

Broadly reactive human CD4+ T cells against Enterobacteriaceae are found in the naïve repertoire and are clonally expanded in the memory repertoire

Enterobacteriaceae are a large family of Gram-negative bacteria that includes both commensals and opportunistic pathogens. The latter can cause severe nosocomial infections, with outbreaks of multi-antibiotics resistant strains, thus being a major public health threat. In this study, we report that Enterobacteriaceae-reactive memory Th cells were highly enriched in a CCR6+ CXCR3+ Th1*/17 cell subset and produced IFN-γ, IL-17A, and IL-22. This T cell subset was severely reduced in septic patients with K. pneumoniae bloodstream infection who also selectively lacked circulating K. pneumonie-reactive T cells. By combining heterologous antigenic stimulation, single cell cloning and TCR Vβ sequencing, we demonstrate that a large fraction of memory Th cell clones was broadly cross-reactive to several Enterobacteriaceae species. These cross-reactive Th cell clones were expanded in vivo and a large fraction of them recognized the conserved outer membrane protein A antigen. Interestingly, Enterobacteriaceae broadly cross-reactive T cells were also prominent among in vitro primed naïve T cells. Collectively, these data point to the existence of immunodominant T cell epitopes shared among different Enterobacteriaceae species and targeted by cross-reactive T cells that are readily found in the pre-immune repertoire and are clonally expanded in the memory repertoire.

Extensively drug-resistant Salmonella Typhi in a patient returning from Pakistan, complicated by relapse with meropenem monotherapy

In developing countries, typhoid fever is a common cause of febrile illness accompanied by abdominal pain and weakness. It is caused by Salmonella enterica serovar Typhi. Humans are the only known reservoir of infection, and typhoid fever is common in regions where access to clean water and sanitation is limited. The antimicrobials of choice for a case of typhoid fever acquired outside Pakistan are third generation cephalosporins. Lately, cases of extensively drug-resistant (XDR) Salmonella Typhi have been reported in people with a travel history to Pakistan. We present a case of XDR typhoid fever which relapsed after treatment with meropenem.

The need & the issues related to new-generation typhoid conjugate vaccines in India

The low- and middle-income countries bear the highest burden of typhoid fever in the world. India, along with other South Asian countries, has a significant incidence of typhoid fever among young children though there is a paucity of published data on community burden. In spite of the availability of Vi-polysaccharide (Vi-PS) and conjugated Vi-PS vaccines, these are not adequately utilized in India and in the neighbouring countries. To address many shortcomings of the unconjugated Vi-PS vaccines, typhoid conjugate vaccines (TCVs) are developed by conjugating Vi-PS with different carrier proteins. Three such vaccines using tetanus toxoid as a carrier protein are already licensed in India. Several other Vi-PS conjugates are currently in various stages of development. The current review provides an update on the existing and upcoming new TCVs along with a detailed discussion on the various issues involved with their clinical use and limitations.

A guide to vaccinology: from basic principles to new developments

Immunization is a cornerstone of public health policy and is demonstrably highly cost-effective when used to protect child health. Although it could be argued that immunology has not thus far contributed much to vaccine development, in that most of the vaccines we use today were developed and tested empirically, it is clear that there are major challenges ahead to develop new vaccines for difficult-to-target pathogens, for which we urgently need a better understanding of protective immunity. Moreover, recognition of the huge potential and challenges for vaccines to control disease outbreaks and protect the older population, together with the availability of an array of new technologies, make it the perfect time for immunologists to be involved in designing the next generation of powerful immunogens. This Review provides an introductory overview of vaccines, immunization and related issues and thereby aims to inform a broad scientific audience about the underlying immunological concepts.

This Review, aimed at a broad scientific audience, provides an introductory guide to the history, development and immunological basis of vaccines, immunization and related issues to provide insight into the challenges facing immunologists who are designing the next generation of vaccines.

Transcutaneous Vaccination with Conjugate Typhoid Vaccine Vi-DT Induces Systemic, Mucosal, and Memory Anti-Polysaccharide Responses

Transcutaneous vaccination can induce both mucosal and systemic immune responses. However, there are few data on anti-polysaccharide responses following transcutaneous vaccination of polysaccharides, despite the role that anti-polysaccharide responses play in protecting against intestinal mucosal and respiratory pathogens. Whether transcutaneous vaccination with a conjugate polysaccharide vaccine would be able to induce memory responses is also unknown. To address this, we transcutaneously vaccinated mice with virulence antigen (Vi) polysaccharide of Salmonella enterica serovar Typhi (the cause of typhoid fever), either in unconjugated or conjugated form (the latter as a Vi-DT conjugate). We also assessed the ability of the immunoadjuvant cholera toxin to impact responses following vaccination. We found that presenting Vi in a conjugate versus nonconjugate form transcutaneously resulted in comparable serum IgG responses but higher serum and lamina propria lymphocyte IgA anti-Vi responses, as well as increased IgG memory responses. The addition of immunoadjuvant did not further increase these responses; however, it boosted fecal IgA and serum IgG anti-Vi responses. Our results suggest that transcutaneous vaccination of a conjugate vaccine can induce systemic as well as enhanced mucosal and memory B-cell anti-polysaccharide responses.

Innate and Adaptive Immune Responses against Bordetella pertussis and Pseudomonas aeruginosa in a Murine Model of Mucosal Vaccination against Respiratory Infection

Whole cell vaccines are frequently the first generation of vaccines tested for pathogens and can inform the design of subsequent acellular or subunit vaccines. For respiratory pathogens, administration of vaccines at the mucosal surface can facilitate the generation of a localized mucosal immune response. Here, we examined the innate and vaccine-induced immune responses to infection by two respiratory pathogens: Bordetella pertussis and Pseudomonas aeruginosa. In a model of intranasal administration of whole cell vaccines (WCVs) with the adjuvant curdlan, we examined local and systemic immune responses following infection. These studies showed that intranasal vaccination with a WCV led to a reduction of the bacterial burden in the airways of animals infected with the respective pathogen. However, there were unique changes in the cytokines produced, cells recruited, and inflammation at the site of infection. Both mucosal vaccinations induced antibodies that bind the target pathogen, but linear regression and principal component analysis revealed that protection from these pathogens is not solely related to antibody titer. Protection from P. aeruginosa correlated to a reduction in lung weight, blood lymphocytes and neutrophils, and the cytokines IL-6, TNF-α, KC/GRO, and IL-10, and promotion of serum IgG antibodies and the cytokine IFN-γ in the lung. Protection from B. pertussis infection correlated strongly with increased anti-B-pertussis serum IgG antibodies. These findings reveal valuable correlates of protection for mucosal vaccination that can be used for further development of both B. pertussis and P. aeruginosa vaccines.

Generation and Characterization of Typhoid Toxin-Neutralizing Human Monoclonal Antibodies

Typhoid toxin is a virulence factor of Salmonella enterica serovar Typhi, the causative agent of typhoid fever, and is thought to be responsible for the symptoms of severe disease. This toxin has a unique A2B5 architecture with two active subunits, the ADP ribosyl transferase PltA and the DNase CdtB, linked to a pentameric B subunit, which is alternatively made of PltB or PltC. Here, we describe the generation and characterization of typhoid toxin-neutralizing human monoclonal antibodies by immunizing genetically engineered mice that have a full set of human immunoglobulin variable region genes. We identified several monoclonal antibodies with strong in vitro and in vivo toxin-neutralizing activity and different mechanisms of toxin neutralization. These antibodies could serve as the basis for the development of novel therapeutic strategies against typhoid fever.

Changes in some haematological parameters in typhoid fever patients attending Landmark University Medical Center, Omuaran-Nigeria

Background

Typhoid or enteric fever is caused by Salmonella typhi. It is largely a disease of developing nations due to poor standard of hygiene and unavailability of potable water. The most prominent feature of the infection is fever which gradually rises to a high plateau. The prevalence of typhoid fever has been on the increase which is associated with several hematological parameters.

Objectives

This study was carried out to determine the changes in various hematological parameters in our study subjects.

Method

Four Hundred- (400) samples were obtained from volunteer subjects visiting the outpatient department of the Landmark University Medical Center. 200 typhoid positive samples were collected from subjects while 200 typhoid negative blood samples served as controls (From both male and female subjects each). Widal test was carried out as a confirmatory test for typhoid fever and evaluation of the hematological parameters were performed. The hematological parameters considered includes Packed Cell Volume (PCV), White Blood Cell count (WBC), Platelet count (PLT), Lymphocyte (LYMP) their implications on both male and female typhoid fever patients were also determined.

Results

The result showed a significant reduction in the values for PCV, WBC, ESR and HAE concentration in typhoid positive males in comparison to typhoid negative males. In females, a significant decrease was observed in values for PCV, ESR, HAE concentration and PLT in typhoid positive females when compared to typhoid negative females. These parameters when compared showed a significant decrease recorded in PCV, ESR and HAE concentration of the typhoid positive male patients in comparison to typhoid positive female patients.

Conclusion

This study implies that anemia, bone marrow suppression and hemaphagocytosis are likely resulting factors of typhoid fever due to the changes in the hematological parameters. Therefore, these parameters have to be further studied to allow for efficient management of this illness.

Assessing the Impact of a Vi-polysaccharide Conjugate Vaccine in Preventing Typhoid Infections Among Nepalese Children: A Protocol for a Phase III, Randomized Control Trial

Background

Enteric fever is estimated to affect 11–20 million people worldwide each year. Morbidity and mortality from enteric fever primarily occur in lower-income countries, with children under 5 years of age experiencing a significant portion of the burden. Over the last few decades, the control of enteric fever has focused primarily on improved water and sanitation, with the available vaccines unsuitable for children and primarily used by travelers. A new typhoid conjugate vaccine (Vi-TCV), prequalified by the World Health Organization (WHO) and highly immunogenic in children under 5, has the potential to reduce the typhoid burden in endemic countries.

Methods

This study is a double-blinded, randomized, controlled trial with a 2-year follow-up to assess the protective impact of the Vi-TCV vaccine, compared with a control vaccine, in children from 9 months to 16 years of age. The primary outcome of interest is the reduction in the number of culture-confirmed typhoid cases attributable to Vi-TCV. Approximately 20 000 children living in the Lalitpur district, within the Kathmandu valley, will be enrolled in the study and followed to measure both safety and efficacy data, which will include adverse events, hospitalizations, antibiotic use, and fever frequency.

Results

Both the intervention and control vaccines are WHO prequalified vaccines, which provide a health benefit to all participants. Children have been chosen to participate because they bear a substantial burden of both typhoid morbidity and mortality in this population. The results of this study will be disseminated through a series of published articles. The findings will also be made available to the participants and the broader community, as well as local stakeholders, within Nepal.

Conclusions

This is the first large-scale, individually randomized, controlled trial of Vi-TCV in children in an endemic setting, and will provide new data on Vi-TCV field efficacy. With Vi-TCV introduction being considered in high-burden countries, this study will support important policy decisions.

Clinical Trials Registration

The trial is registered on the ISRCTN registry (for details, see https://doi.org/10.1186/ISRCTN43385161; registry number: ISRCTN 43385161).

Typhoid Vaccine Acceleration Consortium Malawi: A Phase III, Randomized, Double-blind, Controlled Trial of the Clinical Efficacy of Typhoid Conjugate Vaccine Among Children in Blantyre, Malawi

BACKGROUND

Typhoid fever is an acute infection characterized by prolonged fever following the ingestion and subsequent invasion of Salmonella enterica serovar Typhi (S. Typhi), a human-restricted pathogen. The incidence of typhoid fever has been most reported in children 5-15 years of age, but is increasingly recognized in children younger than 5 years old. There has been a recent expansion of multidrug-resistant typhoid fever globally. Prior typhoid vaccines were not suitable for use in the youngest children in countries with a high burden of disease. This study aims to determine the efficacy of a typhoid conjugate vaccine (TCV) that was recently prequalified by the World Health Organization, by testing it in children 9 months through 12 years of age in Blantyre, Malawi.

METHODS

In this Phase III, individually randomized, controlled, double-blind trial of the clinical efficacy of TCV, 28 000 children 9 months through 12 years of age will be enrolled and randomized in a 1:1 ratio to receive either Vi-TCV or a meningococcal serogroup A conjugate vaccine. A subset of 600 of these children will be further enrolled in an immunogenicity and reactogenicity sub-study to evaluate the safety profile and immune response elicited by Vi-TCV. Recruiting began in February 2018.

RESULTS

All children will be under passive surveillance for at least 2 years to determine the primary outcome, which is blood culture-confirmed S. Typhi illness. Children enrolled in the immunogenicity and reactogenicity sub-study will have blood drawn before vaccination and at 2 timepoints after vaccination to measure their immune response to vaccination. They will also be followed actively for adverse events and serious adverse events.

CONCLUSIONS

The introduction of a single-dose, efficacious typhoid vaccine into countries with high burden of disease or significant antimicrobial resistance could have a dramatic impact, protecting children from infection and reducing antimicrobial usage and associated health inequity in the world's poorest places. This trial, the first of a TCV in Africa, seeks to demonstrate the impact and programmatic use of TCVs within an endemic setting.

CLINICAL TRIALS REGISTRATION

NCT03299426.

Forecasting Demand for the Typhoid Conjugate Vaccine in Low- and Middle-income Countries

BACKGROUND

The World Health Organization (WHO) released a position paper in March 2018 calling for integration of a novel typhoid conjugate vaccine (TCV) into routine immunization along with catch-up campaigns for children up to age 15. Gavi, the Vaccine Alliance, has committed funding to help resource-constrained countries introduce this vaccine. In this article, the Typhoid Vaccine Acceleration Consortium forecasts demand if WHO recommendations are followed.

METHODS

We built a model of global TCV introductions between 2020 and 2040 to estimate the demand of the vaccine for 133 countries. We estimated each country's year of introduction by examining its estimated incidence of typhoid fever, its history of introducing new vaccines, and any knowledge we have of its engagement with typhoid prevention, including intention to apply for Gavi funding. Our model predicted use in routine infant vaccination as well as campaigns targeting varying proportions of the unvaccinated population up to 15 years of age.

RESULTS

Between 2020 and 2025, demand will predominantly come from African countries, many receiving Gavi support. After that, Asian countries generate most demand until 2030, when campaigns are estimated to end. Demand will then track the birth cohort of participating countries, suggesting an annual routine demand between 90 and 100 million doses. Peak demand is likely to occur between 2023 and 2026, approaching 300 million annual doses if campaign implementation is high.

CONCLUSIONS

In our analysis, target population for catch-up campaigns is the main driver of uncertainty. At peak demand, there is some risk of exceeding presently estimated peak production capacity. Therefore, it will be important to carefully coordinate introductions, especially when accompanied by campaigns targeting large proportions of the eligible population.

Acute Gastroenteritis in Children of the World: What Needs to Be Done?

The incidence of gastroenteritis has greatly reduced due to improved hygiene conditions in developing countries and the use of rotavirus vaccine. Still thousands of children, however, die from gastroenteritis, most of them in poor countries. Yet gastroenteritis management is simple, inexpensive, and effective and is largely the same all over the world. Universal guidelines for gastroenteritis guide the management and include simple interventions put forward early in the course of the disease. Treatment includes rehydration, continuing oral feeding, and anti-infective drugs in selected clinical conditions related to the symptoms or to host-related risk, and possible additional drug treatment to reduce the duration and severity of symptoms. There may be minor geographical differences in the treatment applied due to health care organizations that do not substantially change the standard universal recommendations. Prevention is recommended with sanitation interventions and rotavirus universal immunization. Implementation of those interventions through educational initiatives and local programs in target areas are needed. A series of recommendations for interventions, education, and research priorities are included here with the aim of reducing the burden of gastroenteritis, to be pursued by scientists, physicians, policy makers, and stakeholders involved. They include the need of recommendations for the management of gastroenteritis in malnourished children, in those with chronic conditions, in neonates, and in emergency settings. A reference system to score dehydration, the definition of optimal composition of rehydration solution and the indications for anti-infective therapy are also included. Rotavirus immunization should be actively promoted, and evidence-based guidelines should be universally implemented. Research priorities are also indicated.

Progress in the overall understanding of typhoid fever: implications for vaccine development

INTRODUCTION

Typhoid fever continues to have a substantial impact on human health, especially in Asia and sub-Saharan Africa. Access to safe water, and adequate sanitation and hygiene remain the cornerstone of prevention, but these are not widely available in many impoverished settings. The emergence of antibiotic resistance affects typhoid treatment and adds urgency to typhoid control efforts. Vaccines provide opportunities to prevent and control typhoid fever in endemic settings.

AREAS COVERED

Literature search was performed looking for evidence concerning the global burden of typhoid and strategies for the prevention and treatment of typhoid fever. Cost of illness, available typhoid and paratyphoid vaccines and cost-effectiveness were also reviewed. The objective was to provide a critical overview of typhoid fever, in order to assess the current understanding and potential future directions for typhoid treatment and control.

EXPERT COMMENTARY

Our understanding of typhoid burden and methods of prevention has grown over recent years. However, typhoid fever still has a significant impact on health in low and middle-income countries. Introduction of typhoid conjugate vaccines to the immunization schedule is expected to make a major contribution to control of typhoid fever in endemic countries, although vaccination alone is unlikely to eliminate the disease.

Optimizing Vaccination in Adult Patients With Liver Disease and Liver Transplantation

http://aasldpubs.onlinelibrary.wiley.com/hub/journal/10.1002/(ISSN)2046-2484/video/15-2-reading-rhee a video presentation of this article http://aasldpubs.onlinelibrary.wiley.com/hub/journal/10.1002/(ISSN)2046-2484/video/15-2-interview-rhee an interview with the author.

Travel-Related Typhoid Fever: Narrative Review of the Scientific Literature

Enteric fever is a foodborne infectious disease caused by Salmonella enterica serotypes Typhi and Paratyphi A, B and C. The high incidence in low income countries can increase the risk of disease in travelers coming from high income countries. Pre-travel health advice on hygiene and sanitation practices and vaccines can significantly reduce the risk of acquiring infections. Although the majority of the cases are self-limiting, life-threatening complications can occur. Delayed diagnosis and cases of infections caused by multi-drug resistant strains can complicate the clinical management and affect the prognosis. More international efforts are needed to reduce the burden of disease in low income countries, indirectly reducing the risk of travelers in endemic settings. Surveillance activities can help monitor the epidemiology of cases caused by drug-susceptible and resistant strains.

Travelers' Diarrhea: A Clinical Review

Background:

Travelers’ diarrhea is the most common travel-related malady. It affects millions of international travelers to developing countries annually and can significantly disrupt travel plans.

Objective:

To provide an update on the evaluation, diagnosis, treatment, and prevention of traveler’s diar-rhea.

Methods:

A PubMed search was completed in Clinical Queries using the key term “traveler’s diarrhea”. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English literature. Patents were searched using the key term “traveler’s diarrhea” from www.freepatentsonline.com.

Results:

Between 10% and 40% of travelers develop diarrhea. The attack rate is highest for travelers from a developed country who visit a developing country. Children are at particular risk. Travelers’ diarrhea is usually acquired through ingestion of food and water contaminated by feces. Most cases are due to a bac-terial pathogen, commonly, Escherichia coli, and occur within the first few days after arrival in a foreign country. Dehydration is the most common complication. Pretravel education on hygiene and on the safe selection of food items is important in minimizing episodes. For mild travelers’ diarrhea, the use of antibi-otic is not recommended. The use of bismuth subsalicylate or loperamide may be considered. For moder-ate travelers’ diarrhea, antibiotics such as fluoroquinolones, azithromycin, and rifaximin may be used. Loperamide may be considered as monotherapy or adjunctive therapy. For severe travelers’ diarrhea, antibiotics such as azithromycin, fluoroquinolones, and rifaximin should be used. Azithromycin can be used even for the treatment of dysentery whereas fluoroquinolones and rifaximin cannot be used for such purpose. Recent patents related to the management of travelers’ diarrhea are discussed.

Conclusion:

Although travelers’ diarrhea is usually self-limited, many travelers prefer expedient relief of diarrhea, especially when they are traveling for extended periods by air or ground. Judicious use of an antimotility agent and antimicrobial therapy reduces the duration and severity of diarrhea.

Conservation of the OmpC Porin Among Typhoidal and Non-Typhoidal Salmonella Serovars

Salmonella enterica infections remain a challenging health issue, causing significant morbidity and mortality worldwide. Current vaccines against typhoid fever display moderate efficacy whilst no licensed vaccines are available for paratyphoid fever or invasive non-typhoidal salmonellosis. Therefore, there is an urgent need to develop high efficacy broad-spectrum vaccines that can protect against typhoidal and non-typhoidal Salmonella. The Salmonella outer membrane porins OmpC and OmpF, have been shown to be highly immunogenic antigens, efficiently eliciting protective antibody, and cellular immunity. Furthermore, enterobacterial porins, particularly the OmpC, have a high degree of homology in terms of sequence and structure, thus making them a suitable vaccine candidate. However, the degree of the amino acid conservation of OmpC among typhoidal and non-typhoidal Salmonella serovars is currently unknown. Here we used a bioinformatical analysis to classify the typhoidal and non-typhoidal Salmonella OmpC amino acid sequences into different clades independently of their serological classification. Further, our analysis determined that the porin OmpC contains various amino acid sequences that are highly conserved among both typhoidal and non-typhoidal Salmonella serovars. Critically, some of these highly conserved sequences were located in the transmembrane β-sheet within the porin β-barrel and have immunogenic potential for binding to MHC-II molecules, making them suitable candidates for a broad-spectrum Salmonella vaccine. Collectively, these findings suggest that these highly conserved sequences may be used for the rational design of an effective broad-spectrum vaccine against Salmonella.