Seasonal Azithromycin Use in Paediatric Protracted Bacterial Bronchitis Does Not Promote Antimicrobial Resistance but Does Modulate the Nasopharyngeal Microbiome.

Protracted bacterial bronchitis (PBB) causes chronic wet cough for which seasonal azithromycin is increasingly used to reduce exacerbations. We investigated the impact of seasonal azithromycin on antimicrobial resistance and the nasopharyngeal microbiome. In an observational cohort study, 50 children with PBB were enrolled over two consecutive winters; 25/50 at study entry were designated on clinical grounds to take azithromycin over the winter months and 25/50 were not. Serial nasopharyngeal swabs were collected during the study period (12-20 months) and cultured bacterial isolates were assessed for antimicrobial susceptibility. 16S rRNA-based sequencing was performed on a subset of samples. Irrespective of azithromycin usage, high levels of azithromycin resistance were found; 73% of bacteria from swabs in the azithromycin group vs. 69% in the comparison group. Resistance was predominantly driven by azithromycin-resistant S. pneumoniae, yet these isolates were mostly erythromycin susceptible. Analysis of 16S rRNA-based sequencing revealed a reduction in within-sample diversity in response to azithromycin, but only in samples of children actively taking azithromycin at the time of swab collection. Actively taking azithromycin at the time of swab collection significantly contributed to dissimilarity in bacterial community composition. The discrepancy between laboratory detection of azithromycin and erythromycin resistance in the S. pneumoniae isolates requires further investigation. Seasonal azithromycin for PBB did not promote antimicrobial resistance over the study period, but did perturb the microbiome.

The immune evasion roles of Staphylococcus aureus protein A and impact on vaccine development.

While Staphylococcus aureus (S. aureus) bacteria are part of the human commensal flora, opportunistic invasion following breach of the epithelial layers can lead to a wide array of infection syndromes at both local and distant sites. Despite ubiquitous exposure from early infancy, the life-long risk of opportunistic infection is facilitated by a broad repertoire of S. aureus virulence proteins. These proteins play a key role in inhibiting development of a long-term protective immune response by mechanisms ranging from dysregulation of the complement cascade to the disruption of leukocyte migration. In this review we describe the recent progress made in dissecting S. aureus immune evasion, focusing on the role of the superantigen, staphylococcal protein A (SpA). Evasion of the normal human immune response drives the ability of S. aureus to cause infection, often recurrently, and is also thought to be a major hindrance in the development of effective vaccination strategies. Understanding the role of S. aureus virulence protein and determining methods overcoming or subverting these mechanisms could lead to much-needed breakthroughs in vaccine and monoclonal antibody development.

The Challenge Non-Typhoidal Salmonella (CHANTS) Consortium: Development of a non-typhoidal Salmonella controlled human infection model: Report from a consultation group workshop, 05 July 2022, London, UK.

Invasive non-typhoidal Salmonella disease (iNTS) is a major cause of morbidity and mortality globally, particularly as a cause of bloodstream infection in children and immunocompromised adults in sub-Saharan Africa. Vaccines to prevent non-typhoidal Salmonella (NTS) would represent a valuable public health tool in this setting to avert cases and prevent expansion of antimicrobial resistance. Several NTS and combination typhoidal-NTS vaccine candidates are in early-stage development, although the pathway to licensure is unclear due to challenges in conducting large phase III field trials. Controlled human infection models (CHIM) present an opportunity to accelerate vaccine development for a range of enteric pathogens. Several recent typhoidal Salmonella CHIMs have been conducted safely and have played pivotal roles in progressing vaccine candidates to pre-qualification and licensure. The Challenge Non-Typhoidal Salmonella (CHANTS) consortium has been formed with funding from the Wellcome Trust, to deliver the first NTS CHIM, which can act as a platform for future vaccine evaluation. This paper reports the conclusions of a consultation group workshop convened with key stakeholders. The aims of this meeting were to: (1) define the rationale for an NTS CHIM (2) map the NTS vaccine pipeline (3) refine study design and (4) establish potential future use cases.

Early transcriptional responses to human enteric fever challenge.

Enteric fever, caused by oral infection with typhoidal Salmonella serovars, presents as a non-specific febrile illness preceded by an incubation period of 5 days or more. The enteric fever human challenge model provides a unique opportunity to investigate the innate immune response during this incubation period, and how this response is altered by vaccination with the Vi polysaccharide or conjugate vaccine. We find that on the same day as ingestion of typhoidal Salmonella, there is already evidence of an immune response, with 199 genes upregulated in the peripheral blood transcriptome 12 hours post-challenge (false discovery rate <0.05). Gene sets relating to neutrophils, monocytes, and innate immunity were over-represented (false discovery rate <0.05). Estimating cell proportions from gene expression data suggested a possible increase in activated monocytes 12 hours post-challenge (P = 0.036, paired Wilcoxon signed-rank test). Furthermore, plasma TNF-α rose following exposure (P = 0.011, paired Wilcoxon signed-rank test). There were no significant differences in gene expression (false discovery rate <0.05) in the 12 hours response between those who did and did not subsequently develop clinical or blood culture confirmed enteric fever or between vaccination groups. Together, these results demonstrate early perturbation of the peripheral blood transcriptome after enteric fever challenge and provide initial insight into early mechanisms of protection.

The effect of a comprehensive typhoid conjugate vaccine campaign on antimicrobial prescribing in children in Harare, Zimbabwe: a mixed methods study.

BACKGROUND: Vaccines prevent infections and could subsequently reduce antimicrobial use. A 1-week mass vaccination campaign was done with Typbar-TCV (Bharat Biotech, Hyderabad, India) between Feb 25 and March 4, 2019. We investigated whether this typhoid conjugate vaccine campaign could affect antimicrobial prescribing in children presenting to primary care in Harare, Zimbabwe. METHODS: In this mixed methods study, data for acute paediatric outpatient consultations between Jan 1, 2018, and March 31, 2020, were collected from five clinics in Harare. Interrupted time series analysis was done to compare prescription data before and after the campaign. To contextualise findings, qualitative data were collected between April 20, 2021, and July 20, 2022, comprising ethnographic research (ie, workshops, surveys, observations, and interviews) in 14 clinics. Ethnographic data were used for thematic analysis. The primary outcome was monthly antimicrobial prescriptions in children aged 6 months to 15 years, normalised by the number of trauma events in all age groups. FINDINGS: In the data collection period, 27 107 paediatric consultations were recorded. 17 951 (66·2%) of 27 107 children were prescribed antimicrobials. Despite the perceived reduction in typhoid cases and a decreasing trend in the prescription of antimicrobials commonly used to treat typhoid (ie, ciprofloxacin and azithromycin), mass vaccination with Typbar-TCV did not affect the total rate of antimicrobials (adjusted rate ratio, 1·20, 95% CI 0·70-2·05, p=0·51) or the rate of typhoid antimicrobials prescribed (0·93, 0·44-1·96, p=0·85). Unsafe water sources and insufficient diagnostic services were reported to contribute to the continued disease burden and antimicrobial prescription. INTERPRETATION: Non-specific febrile illness caused by confirmed or suspected typhoid is a common cause of antimicrobial use in endemic areas. Although effective in preventing typhoid fever, we were unable to identify any effect of Typbar-TCV on antimicrobial prescribing. Ethnographic research showed the effect of contextual factors on antimicrobial prescribing, including concerns regarding safe water access, appropriate sewage disposal, health-care and diagnostic availability. To realise effects beyond disease burden reduction, holistic approaches addressing these concerns are needed so that the value of vaccines mitigating the effects of antimicrobial use as a driver of antimicrobial resistance is fully achieved. FUNDING: Wellcome Trust. TRANSLATION: For the Shona translation of the abstract see Supplementary Materials section.

Omicron BA.1-containing mRNA-1273 boosters compared with the original COVID-19 vaccine in the UK: a randomised, observer-blind, active-controlled trial.

BACKGROUND: The omicron BA.1 bivalent booster is used globally. Previous open-label studies of the omicron BA.1 (Moderna mRNA-1273.214) booster showed superior neutralising antibody responses against omicron BA.1 and other variants compared with the original mRNA-1273 booster. We aimed to compare the safety and immunogenicity of omicron BA.1 monovalent and bivalent boosters with the original mRNA-1273 vaccine in a large, randomised controlled trial. METHODS: In this large, randomised, observer-blind, active-controlled, phase 3 trial in the UK (28 hospital and vaccination clinic sites), individuals aged 16 years or older who had previously received two injections of any authorised or approved COVID-19 vaccine, with or without an mRNA vaccine booster (third dose), were randomly allocated (1:1) using interactive response technology to receive 50 µg omicron BA.1 monovalent or bivalent vaccines or 50 µg mRNA-1273 administered as boosters via deltoid intramuscular injection. The primary outcomes were safety and immunogenicity at day 29, including prespecified non-inferiority and superiority of booster immune responses, based on the neutralising antibody geometric mean concentration (GMC) ratios of the monovalent and bivalent boosters compared with mRNA-1273. Safety was assessed in all participants who received first or second boosters, and primary immunogenicity outcomes were assessed in all participants who received the planned booster dose, had pre-booster and day 29 antibody data, had no major protocol deviations, and who were SARS-CoV-2-negative. The study is registered with EudraCT (2022-000063-51) and ClinicalTrials.gov (NCT05249829) and is ongoing. FINDINGS: Between Feb 16 and March 24, 2022, 724 participants were randomly allocated to receive omicron BA.1 monovalent (n=366) or mRNA-1273 (n=357), and between April 2 and June 17, 2022, 2824 participants were randomly allocated to receive omicron BA.1 bivalent (n=1418) or mRNA-1273 (n=1395) vaccines as second boosters. Median durations (months) between the most recent COVID-19 vaccine and study boosters were similar for omicron BA.1 monovalent (4·0 months [IQR 3·6-4·7]) and mRNA-1273 (4·1 [3·5-4·7]), and for the omicron BA.1 bivalent (5·5 [4·8-6·2]) and mRNA-1273 (5·4 [4·8-6·2]) boosters. The omicron BA.1 monovalent and bivalent boosters elicited superior neutralising GMCs against the omicron BA.1 variant compared with mRNA-1273, with GMC ratios of 1·68 (99% CI 1·45-1·95) and 1·53 (1·41-1·67) at day 29 post-booster doses in participants without previous SARS-CoV-2 infection. Both boosters induced non-inferior ancestral SARS-CoV-2 (Asp614Gly) immune responses with GMCs that were similar for the bivalent (2987·2 [95% CI 2814·9-3169·9]) versus mRNA-1273 (2911·3 [2750·9-3081·0]) and lower for the monovalent (2699·7 [2431·3-2997·7] vs 3020·6 [2776·5-3286·2]) boosters, with respective GMC ratios of 1·05 (99% CI 0·96-1·15) and 0·82 (95% CI 0·74-0·91). Results were comparable regardless of previous SARS-CoV-2 infection status. Incidences of solicited adverse reactions with the omicron BA.1 monovalent (335 [91·3%] of 367 participants) and omicron BA.1 bivalent (1285 [90·4%] of 1421 participants) boosters were similar to those observed previously for mRNA-1273, with no new safety concerns identified and no occurrences of fatal adverse events. INTERPRETATION: Omicron-containing booster vaccines generated superior immunogenicity against omicron BA.1 and comparable immunogenicity against the original strain with no new safety concerns. It remains important to continuously monitor the immune responses and real-world vaccine effectiveness as divergent SARS-CoV-2 variants emerge. FUNDING: Moderna.

Characterizing altruistic motivation in potential volunteers for SARS-CoV-2 challenge trials.

In human challenge trials (HCTs), volunteers are deliberately infected with an infectious agent. Such trials can be used to accelerate vaccine development and answer important scientific questions. Starting early in the COVID-19 pandemic, ethical concerns were raised about using HCTs to accelerate development and approval of a vaccine. Some of those concerns pertained to potential exploitation of and/or lack of truly informed consent from volunteers. Specific areas of concern arose around individuals who may be unusually risk-seeking or too economically vulnerable to refuse the payments these trials provide, as opposed to being motivated primarily by altruistic goals. This pre-registered study is the first large-scale survey to characterize people who, early in the pandemic, expressed interest and intention to volunteer to participate in COVID-19 HCTs. We found that individuals expressing interest in SARS-CoV-2 HCTs exhibit consistently altruistic motivations without any special indication of poor risk perception or economic vulnerability. In finding that, early in the pandemic, COVID-19 HCTs were able to attract volunteers whose values align with the nature of these trials, and who are not unusually vulnerable to exploitation, this study may allay some ethical concerns about the volunteers interested in participating in such trials.

Treatment of enteric fever (typhoid and paratyphoid fever) with cephalosporins.

BACKGROUND: Typhoid and paratyphoid (enteric fever) are febrile bacterial illnesses common in many low- and middle-income countries. The World Health Organization (WHO) currently recommends treatment with azithromycin, ciprofloxacin, or ceftriaxone due to widespread resistance to older, first-line antimicrobials. Resistance patterns vary in different locations and are changing over time. Fluoroquinolone resistance in South Asia often precludes the use of ciprofloxacin. Extensively drug-resistant strains of enteric fever have emerged in Pakistan. In some areas of the world, susceptibility to old first-line antimicrobials, such as chloramphenicol, has re-appeared. A Cochrane Review of the use of fluoroquinolones and azithromycin in the treatment of enteric fever has previously been undertaken, but the use of cephalosporins has not been systematically investigated and the optimal choice of drug and duration of treatment are uncertain. OBJECTIVES: To evaluate the effectiveness of cephalosporins for treating enteric fever in children and adults compared to other antimicrobials. SEARCH METHODS: We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, the WHO ICTRP and ClinicalTrials.gov up to 24 November 2021. We also searched reference lists of included trials, contacted researchers working in the field, and contacted relevant organizations. SELECTION CRITERIA: We included randomized controlled trials (RCTs) in adults and children with enteric fever that compared a cephalosporin to another antimicrobial, a different cephalosporin, or a different treatment duration of the intervention cephalosporin. Enteric fever was diagnosed on the basis of blood culture, bone marrow culture, or molecular tests. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were clinical failure, microbiological failure and relapse. Our secondary outcomes were time to defervescence, duration of hospital admission, convalescent faecal carriage, and adverse effects. We used the GRADE approach to assess certainty of evidence for each outcome. MAIN RESULTS: We included 27 RCTs with 2231 total participants published between 1986 and 2016 across Africa, Asia, Europe, the Middle East and the Caribbean, with comparisons between cephalosporins and other antimicrobials used for the treatment of enteric fever in children and adults. The main comparisons are between antimicrobials in most common clinical use, namely cephalosporins compared to a fluoroquinolone and cephalosporins compared to azithromycin. Cephalosporin (cefixime) versus fluoroquinolones Clinical failure, microbiological failure and relapse may be increased in patients treated with cefixime compared to fluoroquinolones in three small trials published over 14 years ago: clinical failure (risk ratio (RR) 13.39, 95% confidence interval (CI) 3.24 to 55.39; 2 trials, 240 participants; low-certainty evidence); microbiological failure (RR 4.07, 95% CI 0.46 to 36.41; 2 trials, 240 participants; low-certainty evidence); relapse (RR 4.45, 95% CI 1.11 to 17.84; 2 trials, 220 participants; low-certainty evidence). Time to defervescence in participants treated with cefixime may be longer compared to participants treated with fluoroquinolones (mean difference (MD) 1.74 days, 95% CI 0.50 to 2.98, 3 trials, 425 participants; low-certainty evidence). Cephalosporin (ceftriaxone) versus azithromycin Ceftriaxone may result in a decrease in clinical failure compared to azithromycin, and it is unclear whether ceftriaxone has an effect on microbiological failure compared to azithromycin in two small trials published over 18 years ago and in one more recent trial, all conducted in participants under 18 years of age: clinical failure (RR 0.42, 95% CI 0.11 to 1.57; 3 trials, 196 participants; low-certainty evidence); microbiological failure (RR 1.95, 95% CI 0.36 to 10.64, 3 trials, 196 participants; very low-certainty evidence). It is unclear whether ceftriaxone increases or decreases relapse compared to azithromycin (RR 10.05, 95% CI 1.93 to 52.38; 3 trials, 185 participants; very low-certainty evidence). Time to defervescence in participants treated with ceftriaxone may be shorter compared to participants treated with azithromycin (mean difference of -0.52 days, 95% CI -0.91 to -0.12; 3 trials, 196 participants; low-certainty evidence). Cephalosporin (ceftriaxone) versus fluoroquinolones It is unclear whether ceftriaxone has an effect on clinical failure, microbiological failure, relapse, and time to defervescence compared to fluoroquinolones in three trials published over 28 years ago and two more recent trials: clinical failure (RR 3.77, 95% CI 0.72 to 19.81; 4 trials, 359 participants; very low-certainty evidence); microbiological failure (RR 1.65, 95% CI 0.40 to 6.83; 3 trials, 316 participants; very low-certainty evidence); relapse (RR 0.95, 95% CI 0.31 to 2.92; 3 trials, 297 participants; very low-certainty evidence) and time to defervescence (MD 2.73 days, 95% CI -0.37 to 5.84; 3 trials, 285 participants; very low-certainty evidence). It is unclear whether ceftriaxone decreases convalescent faecal carriage compared to the fluoroquinolone gatifloxacin (RR 0.18, 95% CI 0.01 to 3.72; 1 trial, 73 participants; very low-certainty evidence) and length of hospital stay may be longer in participants treated with ceftriaxone compared to participants treated with the fluoroquinolone ofloxacin (mean of 12 days (range 7 to 23 days) in the ceftriaxone group compared to a mean of 9 days (range 6 to 13 days) in the ofloxacin group; 1 trial, 47 participants; low-certainty evidence). AUTHORS' CONCLUSIONS: Based on very low- to low-certainty evidence, ceftriaxone is an effective treatment for adults and children with enteric fever, with few adverse effects. Trials suggest that there may be no difference in the performance of ceftriaxone compared with azithromycin, fluoroquinolones, or chloramphenicol. Cefixime can also be used for treatment of enteric fever but may not perform as well as fluoroquinolones.  We are unable to draw firm general conclusions on comparative contemporary effectiveness given that most trials were small and conducted over 20 years previously. Clinicians need to take into account current, local resistance patterns in addition to route of administration when choosing an antimicrobial.

Mucosal-Associated Invariant T cells exhibit distinct functional signatures associated with protection against typhoid fever.

We have previously demonstrated that Mucosal-Associated Invariant T (MAIT) cells secrete multiple cytokines after exposure to Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid fever in humans. However, whether cytokine secreting MAIT cells can enhance or attenuate the clinical severity of bacterial infections remain debatable. This study characterizes human MAIT cell functions in subjects participating in a wild-type S. Typhi human challenge model. Here, we found that MAIT cells exhibit distinct functional signatures associated with protection against typhoid fever. We also observed that the cytokine patterns of MAIT cell responses, rather than the average number of cytokines expressed, are more predictive of typhoid fever outcomes. These results might enable us to objectively, based on functional parameters, identify cytokine patterns that may serve as predictive biomarkers during natural infection and vaccination.

Genetic Susceptibility to Enteric Fever in Experimentally Challenged Human Volunteers.

Infections with Salmonella enterica serovars Typhi and Paratyphi A cause an estimated 14 million cases of enteric fever annually. Here, the controlled nature of challenge studies is exploited to identify genetic variants associated with enteric fever susceptibility. Human challenge participants were genotyped by Illumina OmniExpress-24 BeadChip array (n = 176) and/or transcriptionally profiled by RNA sequencing (n = 174). While the study was underpowered to detect any single nucleotide polymorphisms (SNPs) significant at the whole-genome level, two SNPs within CAPN14 and MIATNB were identified with P < 10-5 for association with development of symptoms or bacteremia following oral S. Typhi or S. Paratyphi A challenge. Imputation of classical human leukocyte antigen (HLA) types from genomic and transcriptomic data identified HLA-B*27:05, previously associated with nontyphoidal Salmonella-induced reactive arthritis, as the HLA type most strongly associated with enteric fever susceptibility (P = 0.011). Gene sets relating to the unfolded protein response/heat shock and endoplasmic reticulum-associated protein degradation were overrepresented in HLA-B*27:05+ participants following challenge. Furthermore, intracellular replication of S. Typhi is higher in C1R cells transfected with HLA-B*27:05 (P = 0.02). These data suggest that activation of the unfolded protein response by HLA-B*27:05 misfolding may create an intracellular environment conducive to S. Typhi replication, increasing susceptibility to enteric fever.

Clinical and laboratory factors associated with neonatal sepsis mortality at a major Vietnamese children's hospital.

Sepsis is a major cause of neonatal mortality and children born in low- and middle-income countries (LMICs) are at greater risk of severe neonatal infections than those in higher-income countries. Despite this disparity, there are limited contemporaneous data linking the clinical features of neonatal sepsis with outcome in LMICs. Here, we aimed to identify factors associated with mortality from neonatal sepsis in Vietnam. We conducted a prospective, observational study to describe the clinical features, laboratory characteristics, and mortality rate of neonatal sepsis at a major children's hospital in Ho Chi Minh City. All in-patient neonates clinically diagnosed with probable or culture-confirmed sepsis meeting inclusion criteria from January 2017 to June 2018 were enrolled. We performed univariable analysis and logistic regression to identify factors independently associated with mortality. 524 neonates were recruited. Most cases were defined as late-onset neonatal sepsis and were hospital-acquired (91.4% and 73.3%, respectively). The median (IQR) duration of hospital stay was 23 (13-41) days, 344/524 (65.6%) had a positive blood culture (of which 393 non-contaminant organisms were isolated), and 69/524 (13.2%) patients died. Coagulase-negative staphylococci (232/405; 57.3%), Klebsiella spp. (28/405; 6.9%), and Escherichia coli (27/405; 6.7%) were the most isolated organisms. Sclerema (OR = 11.4), leukopenia <4,000/mm3 (OR = 7.8), thrombocytopenia <100,000/mm3 (OR = 3.7), base excess < -20 mEq/L (OR = 3.6), serum lactate >4 mmol/L (OR = 3.4), extremely low birth weight (OR = 3.2), and hyperglycaemia >180 mg/dL (OR = 2.6) were all significantly (p<0.05) associated with mortality. The identified risk factors can be adopted as prognostic factors for the diagnosis and treatment of neonatal sepsis and enable early risk stratification and interventions appropriate to reduce neonatal sepsis in LMIC settings.

Burden of enteric fever at three urban sites in Africa and Asia: a multicentre population-based study.

BACKGROUND: Enteric fever is a serious public health concern in many low-income and middle-income countries. Numerous data gaps exist concerning the epidemiology of Salmonella enterica serotype Typhi (S Typhi) and Salmonella enterica serotype Paratyphi (S Paratyphi), which are the causative agents of enteric fever. We aimed to determine the burden of enteric fever in three urban sites in Africa and Asia. METHODS: In this multicentre population-based study, we did a demographic census at three urban sites in Africa (Blantyre, Malawi) and Asia (Kathmandu, Nepal and Dhaka, Bangladesh) between June 1, 2016, and Sept 25, 2018. Households were selected randomly from the demographic census. Participants from within the geographical census area presenting to study health-care facilities were approached for recruitment if they had a history of fever for 72 h or more (later changed to >48 h) or temperature of 38·0°C or higher. Facility-based passive surveillance was done between Nov 11, 2016, and Dec 31, 2018, with blood-culture collection for febrile illness. We also did a community-based serological survey to obtain data on Vi-antibody defined infections. We calculated crude incidence for blood-culture-confirmed S Typhi and S Paratyphi infection, and calculated adjusted incidence and seroincidence of S Typhi blood-culture-confirmed infection. FINDINGS: 423 618 individuals were included in the demographic census, contributing 626 219 person-years of observation for febrile illness surveillance. 624 S Typhi and 108 S Paratyphi A isolates were collected from the blood of 12 082 febrile patients. Multidrug resistance was observed in 44% S Typhi isolates and fluoroquinolone resistance in 61% of S Typhi isolates. In Blantyre, the overall crude incidence of blood-culture confirmed S Typhi was 58 cases per 100 000 person-years of observation (95% CI 48-70); the adjusted incidence was 444 cases per 100 000 person-years of observation (95% credible interval [CrI] 347-717). The corresponding rates were 74 (95% CI 62-87) and 1062 (95% CrI 683-1839) in Kathmandu, and 161 (95% CI 145-179) and 1135 (95% CrI 898-1480) in Dhaka. S Paratyphi was not found in Blantyre; overall crude incidence of blood-culture-confirmed S Paratyphi A infection was 6 cases per 100 000 person-years of observation (95% CI 3-11) in Kathmandu and 42 (95% CI 34-52) in Dhaka. Seroconversion rates for S Typhi infection per 100 000 person-years estimated from anti-Vi seroconversion episodes in serological surveillance were 2505 episodes (95% CI 1605-3727) in Blantyre, 7631 (95% CI 5913-9691) in Kathmandu, and 3256 (95% CI 2432-4270) in Dhaka. INTERPRETATION: High disease incidence and rates of antimicrobial resistance were observed across three different transmission settings and thus necessitate multiple intervention strategies to achieve global control of these pathogens. FUNDING: Wellcome Trust and the Bill & Melinda Gates Foundation.

Salmonella Typhi Stool Shedding by Patients With Enteric Fever and Asymptomatic Chronic Carriers in an Endemic Urban Setting.

The burden of Salmonella enterica serotype Typhi (S. Typhi) shedding in stool and its contribution to transmission in endemic settings is unknown. During passive surveillance S. Typhi shedding was seen during convalescence in 332 bacteremic patient with typhoid, although none persisted at 1-year follow-up. Anti-virulence capsule (Vi)-immunoglobulin (Ig) G titers were measured in age-stratified cohort of serosurveillance participants. Systematic stool sampling of 303 participants with high anti-Vi-IgG titers identified 1 asymptomatic carrier with shedding. These findings suggest that ongoing S. Typhi transmission in this setting is more likely to occur from acute convalescent cases, although better approaches are needed to identify true chronic carriers in the community to enable typhoid elimination.

Long-term survivors following autologous haematopoetic stem cell transplantation have significant defects in their humoral immunity against vaccine preventable diseases, years on from transplant.

Current international guidelines recommend routinely vaccinating haematopoetic stem cell transplant (HSCT) recipients. Despite significant infection-related mortality following autologous HSCT, routine vaccination programmes (RVP) completion is poor. For recovered HSCT recipients, it is uncertain whether catch-up vaccination remains worthwhile years later. To determine potential susceptibility to vaccine preventable infections, we measured antibody titres in 56 patients, a median of 7 years (range 0-29) following autologous HSCT, who had not completed RVP. We found that almost all participants had inadequate titres against diphtheria (98.2%) and pneumococcal infection (100%), and a significant proportion had inadequate titres against measles (34.5%). Of those subsequently vaccinated according to available guidelines, many mounted adequate serological responses. These data suggest a pragmatic catch-up approach for autologous HSCT recipients who have not completed RVP is advisable, with universal vaccination against some pathogens (e.g. Streptococcus pneumoniae and diphtheria) and serologically-guided approaches for others (e.g. measles and varicella zoster virus).

Risk factors for SARS-CoV-2 seroprevalence following the first pandemic wave in UK healthcare workers in a large NHS Foundation Trust.

BACKGROUND: We aimed to measure SARS-CoV-2 seroprevalence in a cohort of healthcare workers (HCWs) during the first UK wave of the COVID-19 pandemic, explore risk factors associated with infection, and investigate the impact of antibody titres on assay sensitivity. METHODS: HCWs at Sheffield Teaching Hospitals NHS Foundation Trust (STH) were prospectively enrolled and sampled at two time points. SARS-CoV-2 antibodies were tested using an in-house assay for IgG and IgA reactivity against Spike and Nucleoprotein (sensitivity 99·47%, specificity 99·56%). Data were analysed using three statistical models: a seroprevalence model, an antibody kinetics model, and a heterogeneous sensitivity model. FINDINGS: As of 12th June 2020, 24·4% (n=311/1275) HCWs were seropositive. Of these, 39·2% (n=122/311) were asymptomatic. The highest adjusted seroprevalence was measured in HCWs on the Acute Medical Unit (41·1%, 95% CrI 30·0-52·9) and in Physiotherapists and Occupational Therapists (39·2%, 95% CrI 24·4-56·5). Older age groups showed overall higher median antibody titres. Further modelling suggests that, for a serological assay with an overall sensitivity of 80%, antibody titres may be markedly affected by differences in age, with sensitivity estimates of 89% in those over 60 years but 61% in those ≤30 years. INTERPRETATION: HCWs in acute medical units working closely with COVID-19 patients were at highest risk of infection, though whether these are infections acquired from patients or other staff is unknown. Current serological assays may underestimate seroprevalence in younger age groups if validated using sera from older and/or more symptomatic individuals. RESEARCH IN CONTEXT: Evidence before this study: We searched PubMed for studies published up to March 6th 2021, using the terms "COVID", "SARS-CoV-2", "seroprevalence", and "healthcare workers", and in addition for articles of antibody titres in different age groups against coronaviruses using "coronavirus", "SARS-CoV-2, "antibody", "antibody tires", "COVID" and "age". We included studies that used serology to estimate prevalence in healthcare workers. SARS-CoV-2 seroprevalence has been shown to be greater in healthcare workers working on acute medical units or within domestic services. Antibody levels against seasonal coronaviruses, SARS-CoV and SARS-CoV-2 were found to be higher in older adults, and patients who were hospitalised.Added value of this study: In this healthcare worker seroprevalence modelling study at a large NHS foundation trust, we confirm that those working on acute medical units, COVID-19 "Red Zones" and within domestic services are most likely to be seropositive. Furthermore, we show that physiotherapists and occupational therapists have an increased risk of COVID-19 infection. We also confirm that antibody titres are greater in older individuals, even in the context of non-hospitalised cases. Importantly, we demonstrate that this can result in age-specific sensitivity in serological assays, where lower antibody titres in younger individuals results in lower assay sensitivity.Implications of all the available evidence: There are distinct occupational roles and locations in hospitals where the risk of COVID-19 infection to healthcare workers is greatest, and this knowledge should be used to prioritise infection prevention control and other measures to protect healthcare workers. Serological assays may have different sensitivity profiles across different age groups, especially if assay validation was undertaken using samples from older and/or hospitalised patients, who tend to have higher antibody titres. Future seroprevalence studies should consider adjusting for age-specific assay sensitivities to estimate true seroprevalence rates.

Efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine against SARS-CoV-2 variant of concern 202012/01 (B.1.1.7): an exploratory analysis of a randomised controlled trial.

BACKGROUND: A new variant of SARS-CoV-2, B.1.1.7, emerged as the dominant cause of COVID-19 disease in the UK from November, 2020. We report a post-hoc analysis of the efficacy of the adenoviral vector vaccine, ChAdOx1 nCoV-19 (AZD1222), against this variant. METHODS: Volunteers (aged ≥18 years) who were enrolled in phase 2/3 vaccine efficacy studies in the UK, and who were randomly assigned (1:1) to receive ChAdOx1 nCoV-19 or a meningococcal conjugate control (MenACWY) vaccine, provided upper airway swabs on a weekly basis and also if they developed symptoms of COVID-19 disease (a cough, a fever of 37·8°C or higher, shortness of breath, anosmia, or ageusia). Swabs were tested by nucleic acid amplification test (NAAT) for SARS-CoV-2 and positive samples were sequenced through the COVID-19 Genomics UK consortium. Neutralising antibody responses were measured using a live-virus microneutralisation assay against the B.1.1.7 lineage and a canonical non-B.1.1.7 lineage (Victoria). The efficacy analysis included symptomatic COVID-19 in seronegative participants with a NAAT positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to vaccine received. Vaccine efficacy was calculated as 1 - relative risk (ChAdOx1 nCoV-19 vs MenACWY groups) derived from a robust Poisson regression model. This study is continuing and is registered with ClinicalTrials.gov, NCT04400838, and ISRCTN, 15281137. FINDINGS: Participants in efficacy cohorts were recruited between May 31 and Nov 13, 2020, and received booster doses between Aug 3 and Dec 30, 2020. Of 8534 participants in the primary efficacy cohort, 6636 (78%) were aged 18-55 years and 5065 (59%) were female. Between Oct 1, 2020, and Jan 14, 2021, 520 participants developed SARS-CoV-2 infection. 1466 NAAT positive nose and throat swabs were collected from these participants during the trial. Of these, 401 swabs from 311 participants were successfully sequenced. Laboratory virus neutralisation activity by vaccine-induced antibodies was lower against the B.1.1.7 variant than against the Victoria lineage (geometric mean ratio 8·9, 95% CI 7·2-11·0). Clinical vaccine efficacy against symptomatic NAAT positive infection was 70·4% (95% CI 43·6-84·5) for B.1.1.7 and 81·5% (67·9-89·4) for non-B.1.1.7 lineages. INTERPRETATION: ChAdOx1 nCoV-19 showed reduced neutralisation activity against the B.1.1.7 variant compared with a non-B.1.1.7 variant in vitro, but the vaccine showed efficacy against the B.1.1.7 variant of SARS-CoV-2. FUNDING: UK Research and Innovation, National Institute for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midlands NIHR Clinical Research Network, and AstraZeneca.

Case Report: Typhoid Fever Complicated by Ileal Perforation in an Urban Slum of Dhaka, Bangladesh.

Intestinal perforation is one of the most dangerous complications of typhoid fever and demands urgent hospitalization, diagnosis, and surgical management to reduce morbidity and prevent mortality. Here, we report a case of typhoidal intestinal perforation in a 19 year-old young man detected by passive surveillance during a cluster-randomized trial with Vi-tetanus toxoid conjugate vaccine (Typhoid Vaccine Acceleration Consortium: TyVAC) in an urban slum area in Mirpur, Dhaka, Bangladesh. The patient presented with a high-grade fever, lower abdominal pain, and vomiting and was admitted to a healthcare facility. Physical examination and preoperative investigations of the patient suggested a presumptive diagnosis of intestinal perforation, and the patient was transferred to a tertiary-level hospital for surgical management. A positive blood culture, intraoperative findings, and histopathology of an intestinal biopsy confirmed ileal perforation due to typhoid fever. This case report highlights the need for prompt diagnosis and appropriate pre- and postoperative management of patients who appear with the symptoms of typhoidal intestinal perforation. This report further demonstrates the importance of systematic surveillance and proper evaluation to determine the true incidence rate of typhoid fever and intestinal perforation in Bangladesh.

Single-dose administration and the influence of the timing of the booster dose on immunogenicity and efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine: a pooled analysis of four randomised trials.

BACKGROUND: The ChAdOx1 nCoV-19 (AZD1222) vaccine has been approved for emergency use by the UK regulatory authority, Medicines and Healthcare products Regulatory Agency, with a regimen of two standard doses given with an interval of 4-12 weeks. The planned roll-out in the UK will involve vaccinating people in high-risk categories with their first dose immediately, and delivering the second dose 12 weeks later. Here, we provide both a further prespecified pooled analysis of trials of ChAdOx1 nCoV-19 and exploratory analyses of the impact on immunogenicity and efficacy of extending the interval between priming and booster doses. In addition, we show the immunogenicity and protection afforded by the first dose, before a booster dose has been offered. METHODS: We present data from three single-blind randomised controlled trials-one phase 1/2 study in the UK (COV001), one phase 2/3 study in the UK (COV002), and a phase 3 study in Brazil (COV003)-and one double-blind phase 1/2 study in South Africa (COV005). As previously described, individuals 18 years and older were randomly assigned 1:1 to receive two standard doses of ChAdOx1 nCoV-19 (5 × 1010 viral particles) or a control vaccine or saline placebo. In the UK trial, a subset of participants received a lower dose (2·2 × 1010 viral particles) of the ChAdOx1 nCoV-19 for the first dose. The primary outcome was virologically confirmed symptomatic COVID-19 disease, defined as a nucleic acid amplification test (NAAT)-positive swab combined with at least one qualifying symptom (fever ≥37·8°C, cough, shortness of breath, or anosmia or ageusia) more than 14 days after the second dose. Secondary efficacy analyses included cases occuring at least 22 days after the first dose. Antibody responses measured by immunoassay and by pseudovirus neutralisation were exploratory outcomes. All cases of COVID-19 with a NAAT-positive swab were adjudicated for inclusion in the analysis by a masked independent endpoint review committee. The primary analysis included all participants who were SARS-CoV-2 N protein seronegative at baseline, had had at least 14 days of follow-up after the second dose, and had no evidence of previous SARS-CoV-2 infection from NAAT swabs. Safety was assessed in all participants who received at least one dose. The four trials are registered at ISRCTN89951424 (COV003) and ClinicalTrials.gov, NCT04324606 (COV001), NCT04400838 (COV002), and NCT04444674 (COV005). FINDINGS: Between April 23 and Dec 6, 2020, 24 422 participants were recruited and vaccinated across the four studies, of whom 17 178 were included in the primary analysis (8597 receiving ChAdOx1 nCoV-19 and 8581 receiving control vaccine). The data cutoff for these analyses was Dec 7, 2020. 332 NAAT-positive infections met the primary endpoint of symptomatic infection more than 14 days after the second dose. Overall vaccine efficacy more than 14 days after the second dose was 66·7% (95% CI 57·4-74·0), with 84 (1·0%) cases in the 8597 participants in the ChAdOx1 nCoV-19 group and 248 (2·9%) in the 8581 participants in the control group. There were no hospital admissions for COVID-19 in the ChAdOx1 nCoV-19 group after the initial 21-day exclusion period, and 15 in the control group. 108 (0·9%) of 12 282 participants in the ChAdOx1 nCoV-19 group and 127 (1·1%) of 11 962 participants in the control group had serious adverse events. There were seven deaths considered unrelated to vaccination (two in the ChAdOx1 nCov-19 group and five in the control group), including one COVID-19-related death in one participant in the control group. Exploratory analyses showed that vaccine efficacy after a single standard dose of vaccine from day 22 to day 90 after vaccination was 76·0% (59·3-85·9). Our modelling analysis indicated that protection did not wane during this initial 3-month period. Similarly, antibody levels were maintained during this period with minimal waning by day 90 (geometric mean ratio [GMR] 0·66 [95% CI 0·59-0·74]). In the participants who received two standard doses, after the second dose, efficacy was higher in those with a longer prime-boost interval (vaccine efficacy 81·3% [95% CI 60·3-91·2] at ≥12 weeks) than in those with a short interval (vaccine efficacy 55·1% [33·0-69·9] at <6 weeks). These observations are supported by immunogenicity data that showed binding antibody responses more than two-fold higher after an interval of 12 or more weeks compared with an interval of less than 6 weeks in those who were aged 18-55 years (GMR 2·32 [2·01-2·68]). INTERPRETATION: The results of this primary analysis of two doses of ChAdOx1 nCoV-19 were consistent with those seen in the interim analysis of the trials and confirm that the vaccine is efficacious, with results varying by dose interval in exploratory analyses. A 3-month dose interval might have advantages over a programme with a short dose interval for roll-out of a pandemic vaccine to protect the largest number of individuals in the population as early as possible when supplies are scarce, while also improving protection after receiving a second dose. FUNDING: UK Research and Innovation, National Institutes of Health Research (NIHR), The Coalition for Epidemic Preparedness Innovations, the Bill & Melinda Gates Foundation, the Lemann Foundation, Rede D'Or, the Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca.