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Roles and responsibilities of participants, researchers, and the media in the communication of vaccine trials: Experience from the United Kingdom's first COVID-19 vaccine trial.
BACKGROUND: The media have played an important part in presenting arguments for and against vaccination. The potential for the media to influence public attitudes to vaccines is becoming increasingly crucial to address. METHODS: To understand the differing roles and responsibilities in the communication of vaccine trials we draw insight from a retrospective study of 349 survey responses and 102 semi-structured interviews conducted in 2020 with participants in the United Kingdom's first-in-human clinical trial of the Oxford-AstraZeneca COVID-19 vaccine. RESULTS: We found that trial participants had mixed views as to whether their participation conferred responsibility to communicate more widely about their trial experiences. Some participants perceived themselves to have an altruistic obligation to communicate to the media about the trial, and others felt that those who did share their participation had 'attention-seeking' motives. When participants did speak out they preferred to do so anonymously. Frustration was also reported with sensationalised and false media stories. Social media was viewed as a means to accelerate misinformation or as a force for recruitment and public education about trials. Participants were pleased to see trial investigators and trial team playing prominent roles in the media and this instilled confidence in the vaccine and the trial. We discuss these evolving roles and responsibilities for trial communication, concentrating on the views of participants about experiences, opportunities, and risks. CONCLUSIONS: We argue that the pandemic has demonstrated the need for clinical trials to be made more transparent as a scientific practice that requires better public understanding and engagement. For high-profile vaccine trials we recommend; (1) explicit and comprehensive guidance aimed at all participants for interactions with the media; (2) prioritising having open and effectively expressed accounts of trial composition, processes, and participation; (3) offering support and a direct communication channel for journalists to report trials by utilising internal press officers to engage with journalists.
Implementation and adherence to regular asymptomatic testing in a COVID-19 vaccine trial.
BACKGROUND: For pathogens which cause infections that present asymptomatically, evaluating vaccine efficacy (VE) against asymptomatic infection is important for understanding a vaccine's potential epidemiological impact. Regular testing for subclinical infections is a potentially valuable strategy but its success hinges on participant adherence and minimising false positives. This paper describes the implementation and adherence to weekly testing in a COVID-19 vaccine trial. METHODS: COV002 was a phase 2/3 trial assessing the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2. Asymptomatic infections were detected using weekly self-administered swabs for RT-PCR testing. We analysed adherence using mixed-effects regression models and estimated the probability of true and false positive asymptomatic infections using estimates of adherence and testing characteristics. FINDINGS: 356,551 tests were self-administered by 10,811 participants during the 13-month follow-up. Median adherence was 75.0% (IQR 42·6-90·9), which translated to a 74·5% (IQR 50·9-78·8) probability of detecting a positive asymptomatic infection during the swabbing period, and between 21 and 96 false positives during VE evaluation. The odds of returning a swab declined by 8% per week and further after testing positive and unblinding. Adherence was higher in older age groups, females and non-healthcare workers. INTERPRETATION: The COV002 trial demonstrated the feasibility of running a long-term regular asymptomatic testing strategy. This information could be valuable for designing future phase III vaccine trials in which infection is an outcome. FUNDING: UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, AstraZeneca.
Influence of Dystrophin Isoform Deficiency on Motor Development in Duchenne Muscular Dystrophy.
OBJECTIVE: In Duchenne muscular dystrophy (DMD), lack of the shorter dystrophin isoforms Dp140 and Dp71 is associated with increased central nervous system (CNS) involvement. We aimed to investigate how CNS involvement affects motor development in young DMD boys. METHOD: Three hundred and forty-two DMD boys aged 3-6 years were subdivided according to DMD mutation expected effects on isoform expression: Group 1 (Dp427 absent, Dp140/Dp71 present, n = 170); Group 2 (Dp427/Dp140 absent, Dp71 present, n = 154) and Group 3 (Dp427/Dp140/Dp71 absent, n = 18). Mixed effects logistic regression was used to investigate relationships between isoform group and the odds of achieving higher North Star Ambulatory Assessment (NSAA) subitem scores for 15 subitems, adjusting for age at visit and glucocorticoid exposure. RESULTS: The odds of achieving a full score of 2 were significantly lower for 11 NSAA subitems in Group 2 compared to Group 1, 5 NSAA subitems in Group 3 compared to Group 1, and 2 NSAA subitems in Group 3 compared to Group 2. The odds of achieving a score of 2 or 1 compared to 0 were significantly lower in Group 2 compared to Group 1 for the 2 NSAA subitems studied using this comparison. INTERPRETATION: We found strong and significant associations between the odds of achieving higher NSAA subitem scores and expected patterns of dystrophin isoform involvement, with a cumulative effect of loss of isoforms. This suggests an important relationship between dystrophin isoforms in the brain and the ability to carry out gross motor milestones.
From marker to markerless: Validating DeepLabCut for 2D sagittal plane gait analysis in adults and newly walking toddlers
The use of 3D marker-based motion analysis systems is considered the gold standard for tracking limb movements. However, these systems are expensive, limited to laboratory settings, and difficult to apply when studying paediatric populations. Therefore, this study investigated the validity of a markerless motion tracking software, DeepLabCut, in extracting kinematics from 2D sagittal plane videos of adults and toddlers during walking. Data were obtained from fifteen toddlers performing their first independent steps and sixteen healthy adults. Participants performed overground and treadmill walking at comfortable pace. Distinct models with either 25% or 75% of participants as input were used for DeepLabCut network training. For all participants, anatomical landmarks extracted through video analysis in DeepLabCut were used to calculate lower-limb gait kinematics, which were compared to kinematics computed using a 3D marker-based system (Vicon). The 25% models performed well for adult joint angles, but not for clinical parameters or toddlers. In both populations, the 75% models showed good (≥0.60) or excellent (≥0.75) intraclass correlation coefficient absolute agreement for most time-normalized joint angles and clinical parameters. This improvement was supported by increased Pearson's correlation coefficients, decreased root mean squared errors, and increased R2 values from the 25% to the 75% models. More specifically, higher validity of DeepLabCut was found for adults compared to toddlers and treadmill compared to overground walking. Altogether, with sufficiently diverse input, DeepLabCut proved a valid tool to acquire gait kinematics in known scenarios, with the potential to study typical adult and toddler gait in more ecological and naturalistic environments.
Exploring the cortical involvement in sensorimotor integration during early stages of independent walking.
The control of human locomotion is governed by a combination of congenital and emerging locomotor muscle synergies. The first arguably build on spinal and brainstem circuitries, whereas the latter have a cortical resemblance. By hypothesis this cortical activity reflects sensorimotor integration which matures during the development of walking. We therefore investigated the role of sensory information by manipulating the gravitational loading in 23 toddlers walking on an instrumented treadmill while recording 3D kinematics, EEG, and EMG of 24 trunk and lower extremity muscles. Sensory loading was manipulated via low and high levels of external body weight support. Cortico-synergy connectivity was compared between the two different support levels and at two stages of gait development: onset of independent walking (just after the first steps) and at six months of walking experience. These two age groups consisted of different subjects. For twelve toddlers data quantity and quality met requirements to enter analysis. Four muscle synergies sufficed to characterise gait, regardless of support level and developmental stage. Cortico-synergy coherence confirmed involvement of the sensorimotor cortex only in the two emerging synergies associated with walking onset. Reduced sensory loading was accompanied by a decreased coherence but only in toddlers with little walking experience. That gravitational loading alters the cortical resemblance of the synergies, especially at an early age, suggests that it reflects the integration of sensory information, at least to some extent. Our findings hint at the importance of sensorimotor integration in the emergence of the synergies linked to the onset of independent walking.
Clinical significance of preleukemic somatic GATA1 mutations in children with Down syndrome.
Children with Down syndrome (DS) have a high risk of GATA1-associated myeloid leukemia (ML-DS) before age 4. Somatic N-terminal GATA1 mutations (GATA1s) are necessary, but not sufficient, for ML-DS, but their significance at birth for individual babies and whether mutations occur after birth is unclear. To address these questions, we performed a prospective study of DS newborns using next-generation sequencing-based GATA1 mutation analysis with detailed hematologic and clinical evaluation and follow-up for the window of ML-DS risk. Of 450 DS neonates, 113 (25%) had GATA1s mutations of which 20/113 (17.7%) were multiple and 59 (52%) were clinically silent. Variant allele frequency (VAF) varied from 0.3-89%. VAF positively correlated (p<0.0001) with % blasts, leukocytes, dyserythro- and dysmegakaryopoiesis scores and clinical disease and negatively with hemoglobin, although only 4/113 were anemic. GATA1s mutations were detected from 28 weeks(w) gestation; the highest frequency (45%) was at 34-35w while mutation frequency in early fetal samples (<20w) was only <4% (2/57). GATA1s clones (VAF, % blasts) fell rapidly post-natally becoming undetectable by 6 months (6m) except in neonates who developed ML-DS. 7/110 surviving neonates (6.4%) developed ML-DS at a median age of 17.5m. GATA1s clone size at birth was the only predictor of subsequent ML-DS. No neonates lacking GATA1s mutations acquired mutations after birth or developed ML-DS. Taken together, the fetal environment is essential for GATA1s mutation selection and expansion of GATA1s clones. Rates of leukemic transformation of GATA1s clones detected at birth are low but clones that persist beyond 6 months transformed.
The use of controlled human infection models to identify correlates of protection for invasive Salmonella vaccines.
Controlled human infection model (CHIM) studies, which involve deliberate exposure of healthy human volunteers to an infectious agent, are recognised as important tools to advance vaccine development. These studies not only facilitate estimates of vaccine efficacy, but also offer an experimental approach to study disease pathogenesis and profile vaccine immunogenicity in a controlled environment, allowing correlation with clinical outcomes. Consequently, the data from CHIMs can be used to identify immunological correlates of protection (CoP), which can help accelerate vaccine development. In the case of invasive Salmonella infections, vaccination offers a potential instrument to prevent disease. Invasive Salmonella disease, caused by the enteric fever pathogens Salmonella enterica serovar Typhi (S. Typhi) and S. Paratyphi A, B and C, and nontyphoidal Salmonella (iNTS), remains a significant cause of mortality and morbidity in low- and middle-income countries, resulting in over 200,000 deaths and the loss of 15 million DALYs annually. CHIM studies have contributed to the understanding of S. Typhi infection and provided invaluable insight into the development of vaccines and CoP following vaccination against S. Typhi. However, CoP are less well understood for S. Paratyphi A and iNTS. This brief review focuses on the contribution of vaccine-CHIM trials to our understanding of the immune mechanisms associated with protection following vaccines against invasive Salmonella pathogens, particularly in relation to CoP.
Acute Plasmodium yoelii 17XNL Infection During BCG Vaccination Limits T Cell Responses and Mycobacterial Growth Inhibition.
Tuberculosis and malaria overlap in many sub-Saharan African countries where Bacillus Calmette Guérin (BCG) vaccination is routinely administered. The aim of this study was to determine whether the timing of BCG vaccination in relation to a malaria infection has implications for BCG vaccine efficacy. Mice were intradermally vaccinated with BCG either 4 weeks before infection with blood-stage Plasmodium yoelii 17XNL, at 13 days post-infection (during an acute blood-stage malaria infection) or 21 days post-infection (after clearance of P. yoelii 17XNL infection). Ex vivo control of mycobacterial growth by splenocytes was used as a surrogate of protective efficacy, and PPD-specific T-cell responses were quantified by flow cytometry. No differences in mycobacterial growth control were detected between BCG vaccinated mice and groups receiving vaccination prior to or after clearance of P. yoelii 17XNL infection. Poorer control of mycobacterial growth was observed following BCG vaccination administered during an acute malarial infection compared to BCG vaccination only or BCG vaccination after blood-stage malaria infection, and mycobacterial growth negatively correlated with the magnitude of total cytokine production from PPD-specific CD4+ T cells (p
The waning of maternal measles antibodies: a multi-country maternal-infant seroprevalence study.
OBJECTIVES: To assess geographical variation in maternal measles antibody levels from birth to nine months of age, to inform recommendations for the timing of first measles vaccine dose. METHODS: Stored infant serum samples from 11 countries taken at delivery and/or follow-up time points prior to measles vaccination (N=2,845) were tested for measles plaque reduction neutralisation (PRNT) and measles, mumps, and rubella immunoglobulin G at a central laboratory. Antibody decay in infants was modelled using linear mixed effects models with participant-level random intercepts and random slopes. Proportions of infants with antibody concentrations above the clinical protection threshold (0.12 IU/mL) were estimated at each age. RESULTS: At birth most (94%, 519/552) infants had PRNT ≥0.12 IU/mL, but geometric mean concentrations ranged 0.32 IU/mL (Guatemala) to 1.60 IU/mL (Pakistan). There was no geographical variation in decay rate of PRNT nor immunoglobulin G. Geometric mean PRNT fell below 0.12 IU/mL between ages 2.5 months (Guatemala) and 6.2 months (Pakistan). At age 6 months <50% of infants had PRNT ≥0.12 IU/mL in all countries except Pakistan. CONCLUSIONS: Reliance on maternal antibodies for protection until age 9 months or later leaves most infants with insufficient direct protection against measles infection between ages 6-9 months.
The emergence of Fanconi anaemia type S: a phenotypic spectrum of biallelic BRCA1 mutations.
BRCA1 is involved in the Fanconi anaemia (FA) pathway, which coordinates repair of DNA interstrand cross-links. FA is a rare genetic disorder characterised by bone marrow failure, cancer predisposition and congenital abnormalities, caused by biallelic mutations affecting proteins in the FA pathway. Germline monoallelic pathogenic BRCA1 mutations are known to be associated with hereditary breast/ovarian cancer, however biallelic mutations of BRCA1 were long predicted to be incompatible with embryonic viability, hence BRCA1 was not considered to be a canonical FA gene. Despite this, several patients with biallelic pathogenic BRCA1 mutations and FA-like phenotypes have been identified - defining a new FA type (FA-S) and designating BRCA1 as an FA gene. This report presents a scoping review of the cases of biallelic BRCA1 mutations identified to date, discusses the functional effects of the mutations identified, and proposes a phenotypic spectrum of BRCA1 mutations based upon available clinical and genetic data. We report that this FA-S cohort phenotype includes short stature, microcephaly, facial dysmorphisms, hypo/hyperpigmented lesions, intellectual disability, chromosomal sensitivity to crosslinking agents and predisposition to breast/ovarian cancer and/or childhood cancers, with some patients exhibiting sensitivity to chemotherapy. Unlike most other types of FA, FA-S patients lack bone marrow failure.
Clinical variants in Caenorhabditis elegans expressing human STXBP1 reveal a novel class of pathogenic variants and classify variants of uncertain significance
Purpose: Modeling disease variants in animals is useful for drug discovery, understanding disease pathology, and classifying variants of uncertain significance (VUS) as pathogenic or benign. Methods: Using Clustered Regularly Interspaced Short Palindromic Repeats, we performed a Whole-gene Humanized Animal Model procedure to replace the coding sequence of the animal model's unc-18 ortholog with the coding sequence for the human STXBP1 gene. Next, we used Clustered Regularly Interspaced Short Palindromic Repeats to introduce precise point variants in the Whole-gene Humanized Animal Model–humanized STXBP1 locus from 3 clinical categories (benign, pathogenic, and VUS). Twenty-six phenotypic features extracted from video recordings were used to train machine learning classifiers on 25 pathogenic and 32 benign variants. Results: Using multiple models, we were able to obtain a diagnostic sensitivity near 0.9. Twenty-three VUS were also interrogated and 8 of 23 (34.8%) were observed to be functionally abnormal. Interestingly, unsupervised clustering identified 2 distinct subsets of known pathogenic variants with distinct phenotypic features; both p.Tyr75Cys and p.Arg406Cys cluster away from other variants and show an increase in swim speed compared with hSTXBP1 worms. This leads to the hypothesis that the mechanism of disease for these 2 variants may differ from most STXBP1-mutated patients and may account for some of the clinical heterogeneity observed in the patient population. Conclusion: We have demonstrated that automated analysis of a small animal system is an effective, scalable, and fast way to understand functional consequences of variants in STXBP1 and identify variant-specific intensities of aberrant activity suggesting a genotype-to-phenotype correlation is likely to occur in human clinical variations of STXBP1.
miR-107 represses DMPK and is sequestered by CUG repeats triggering the MSI2/miR-7 pathogenesis axis in myotonic dystrophy
Myotonic dystrophy type 1 (DM1) is a multisystem genetic disorder characterized by muscle disease, including muscle atrophy partially originating from excessive autophagy. We have previously demonstrated that excessive Musashi-2 (MSI2) repressed the biogenesis of miR-7, which derepressed autophagy, ultimately contributing to muscle atrophy, but the root cause of MSI2 dysregulation is unknown. Herein, we investigate the intricate role of miR-107 in DM1 pathogenesis, focusing on its involvement in the MSI2>miR-7>autophagy axis as this microRNA (miRNA) directly regulates MSI2. We found that in DM1, miR-107 function is impaired because expanded CUG repeats sequester it, causing an increase in the expression of its targets, including MSI2. Through different experimental approaches, including luciferase reporter assays, differential scanning fluorimetry, and electrophoretic mobility shift assay (EMSA), we confirm that miR-107 directly binds to CUG repeats in mutant DMPK transcripts. DMPK posttranscriptional regulation by miR-107 was also demonstrated. Modulation of miR-107 in a DM1 cell model context significantly affects its downstream targets, MSI2 and miR-7, thus decreasing excessive autophagic markers and restoring pathological phenotypes such as ribonuclear foci and impaired fusion capacity. These findings underscore the critical role of miR-107 in regulating the MSI2>miR-7>autophagy axis and support this miRNA as a promising therapeutic target for correcting muscle dysfunction in DM1.
Respiratory viral detection in children hospitalized with pneumonia during periods of major population disruptions in Nepal, 2014-2018.
BACKGROUND: Respiratory viruses commonly cause pneumonia in children. We aimed to identify respiratory viral nucleic acids in the nasopharynx of children admitted with pneumonia from 2014 to 2018, a period including a major earthquake (April 2015), PCV10 introduction (August 2015), and a fuel shortage (October 2015 to March 2016). METHODS: Children 2 months to 14 years admitted to Patan Hospital between March 2014 and February 2018 with a clinical diagnosis of pneumonia had nasopharyngeal swabs collected and tested with a multiplex panel for the presence of genetic material from 23 respiratory pathogens. RESULTS: Of 1343 children with pneumonia, 974 (72.5%) had the nucleic acids of at least one respiratory virus in the nasopharynx. The median age of children with any viral genetic material detected was lower than those without (1.18, IQR: 0.59-2.39 years; versus 2.01 years, IQR: 0.81-4.34 years; p<0.001). Commonly detected viral nucleic acids included those of RSV (21.0%), rhino/enterovirus (30.8%), and parainfluenza (7.4%). The odds of detecting any respiratory viral genetic material in children with pneumonia increased by 1.88 (95% confidence interval: 1.15, 3.06) in the year after the earthquake, when there were several aftershocks and a fuel crisis, relative to other periods and accounting for other potential confounding factors. CONCLUSIONS: These findings highlight the importance of viral diagnostics in pediatric pneumonia and suggest that public health measures addressing environmental conditions during disasters might help reduce respiratory infections.
LISTEN: lived experiences of Long COVID: a social media analysis of mental health and supplement use
IntroductionLong COVID, or Post-Acute Sequelae of SARS-CoV-2 infection (PASC), is a complex condition characterized by a wide range of persistent symptoms that can significantly impact an individual's quality of life and mental health. This study explores public perspectives on the mental health impact of Long COVID and the use of dietary supplements for recovery, drawing on social media content. It uniquely addresses how individuals with Long COVID discuss supplement use in the absence of public health recommendations.MethodsThe study employs the LISTEN method (“Collaborative and Digital Analysis of Big Qual Data in Time Sensitive Contexts”), an interdisciplinary approach that combines human insight and digital analysis software. Social media data related to Long COVID, mental health, and supplement use were collected using the Pulsar Platform. Data were analyzed using the free-text discourse analysis tool Infranodus and collaborative qualitative analysis methods.ResultsThe findings reveal key themes, including the impact of Long COVID on mental health, occupational health, and the use of food supplements. Analysis of attitudes toward supplement use highlights the prevalence of negative emotions and experiences among Long COVID patients. The study also identifies the need for evidence-based recommendations and patient education regarding supplement use.DiscussionThe findings contribute to a better understanding of the complex nature of Long COVID and inform the development of comprehensive, patient-centered care strategies addressing both physical and mental health needs.
What is the current evidence base for measles vaccination earlier than 9 months of age?: Report from an informal technical consultation of the World Health Organization.
Measles is one of the most contagious vaccine preventable diseases, causing severe complications and deaths globally. While vaccination with a measles-containing vaccine (MCV) has prevented millions of measles deaths, recent trends, especially from low- and middle-income countries, are discouraging. Measles cases have increased since 2021 as MCV coverage has decreased; and an estimated 107,500 measles deaths, mostly in children under-five years, occurred in 2023. Thus, a renewed focus on proven and innovative strategies to control measles is needed. The World Health Organization (WHO) recommends a first MCV dose administered at 9-15 months of age (routine MCV1), however MCV1 below 9 months of age (early MCV1) may increase vaccination coverage because uptake of all vaccines tends to be higher the younger the child, and this might protect vulnerable infants earlier in life. However, due to concerns about possible reduced vaccine performance, early MCV1 is not routinely recommended by WHO. WHO hosted an informal technical consultation on December 6-7, 2023, in Geneva, Switzerland to evaluate recent evidence on early MCV1 and identify evidence gaps for policy making. The recent evidence suggests a robust humoral immune response shortly after early MCV1 at 5-8 months of age. Immune blunting of a routine second MCV dose (e.g., MCV2) after early MCV1 was not demonstrated in the presented data. However, 3-7 years after MCV1, children receiving early MCV1 had lower measles antibodies than children receiving routine MCV1, suggesting faster waning of immunity. The totality of evidence on immune blunting remains inconsistent. Meeting participants thought more data are needed before revisiting WHO's current recommendation for a potential revision. Evidence gaps include: understanding measles disease burden and severity in infants; early MCV1 effectiveness and duration; vaccine-induced cellular immunogenicity; whether measles in infants is acquired from other infants or older children or adults; and blunting of routine MCV2. Addressing evidence gaps through targeted studies and measles outbreak investigations, as well as evaluations of country-level introductions of early MCV1 are warranted. Ensuring high MCV1 and MCV2 coverage remains the priority in measles control.
Seroprevalence of Cytomegalovirus Among Pregnant Women at Kawempe National Referral Hospital, Uganda: A Cross-sectional Study.
BACKGROUND: Maternal primary cytomegalovirus (CMV) infection is associated with abortion and congenital anomalies. In Uganda, the burden of maternal CMV infection is not well studied. This study thus assessed the seroprevalence and factors associated with CMV infection among pregnant women at Kawempe National Referral Hospital in Kampala. This work forms a part of the PROGRESS study, an observational cohort study undertaken in Kampala, Uganda, between November 2018 and April 2021. METHODS: We conducted a cross-sectional study between September 2020 and January 2021 among the 639 pregnant women admitted to the labor ward at a government hospital. Sociodemographic, medical, obstetric, and socioeconomic data were collected. Blood samples from study participants were drawn and analyzed for the presence of CMV immunoglobulin G (IgG) and IgM using enzyme-linked immunosorbent assay-based quantitative assays. Further analysis of all IgM-positive samples was conducted using CMV IgG avidity assays. All infants had a nasal polymerase chain reaction (PCR) on the first day of life to investigate CMV positivity. Logistic regression was performed to determine the factors associated with CMV infection. RESULTS: Seroprevalence of CMV IgG among the 637 women was universal (100%), and that of CMV (IgM) was 5.8% (37/637). CMV (IgM) was associated with being low socioeconomic status (odds ratio, 3.44; 95% CI, 1.05-11.32; P = .04). Transmission risk was low, and no infant had a positive PCR for CMV at birth. CONCLUSIONS: Universally, by the time women in Kampala conceive, they will have been exposed to CMV. Women of lower socioeconomic status were more likely to have recent CMV infection than their more affluent counterparts, highlighting the need for screening guidelines in this setting.
The validity of test-negative design for assessment of typhoid conjugate vaccine protection: comparison of estimates by different study designs using data from a cluster-randomised controlled trial.
BACKGROUND: Typhoid fever remains a substantial public health challenge in low-income and middle-income countries. By 2023, typhoid conjugate vaccines (TCVs) had been introduced in six countries globally, with more than 50 million doses distributed. Now that TCVs are being deployed, there is a need for observational studies to assess vaccine effectiveness in the field. We aimed to evaluate the validity of different observational study designs in estimating vaccine protection. METHODS: We compared different observational and experimental study designs for assessing vaccine effectiveness by re-analysing data from the TyVAC Bangladesh trial, a participant-blinded and observer-blinded cluster-randomised controlled trial done in Mirpur, Dhaka, Bangladesh. 150 geographical clusters were randomly assigned (1:1) to receive either TCV or Japanese encephalitis vaccine. Eligible children aged 9 months to 15 years were offered a single dose of the vaccine randomly assigned to their cluster of residence, and baseline vaccination was done between April 15 and May 15, 2018. We compared estimates of vaccine effectiveness from the cluster-randomised controlled trial analysis-which assessed the risk of blood-culture-confirmed typhoid fever among recipients of TCV versus recipients of Japanese encephalitis vaccine-with estimates from cohort study and test-negative case-control study design (TND) analyses, which compared recipients of TCV with non-vaccinees in the 75 geographical clusters where TCV was administered. We further conducted negative-control exposure (NCE) and negative-control outcome (NCO) analyses as bias indicators. FINDINGS: 41 344 (67%) of 62 025 age-eligible children in the study area received the TCV or Japanese encephalitis vaccine during the baseline vaccination campaign. Among the 62 025 age-eligible children, 5582 blood-culture specimens were collected by passive surveillance, including 2546 (46%) specimens from the 75 TCV clusters. The estimated vaccine efficacy was 89% (95% CI 81-93) in the cluster-randomised controlled trial analysis, 79% (70-86) by the cohort design, 88% (79-93) by the TND when pan-negatives were used as test-negative controls, and 90% (75-96) by the TND when specimens positive for pathogens other than Salmonella enterica serotype Typhi were used as test-negative controls. Using NCE analysis, Japanese encephalitis vaccination was associated with an increased risk of typhoid fever compared with non-vaccinees in the 75 Japanese encephalitis clusters in the cohort design (incidence rate ratio 1·98 [95% CI 1·56-2·52]), but no significant association between Japanese encephalitis vaccination and typhoid fever was found with the TND. Similarly, an increased risk of non-typhoid infections was observed in the cohort NCO analyses when comparing vaccinees with non-vaccinees in both Japanese encephalitis vaccine clusters and TCV clusters, but not in the TND NCO analyses. INTERPRETATION: Our findings suggests that the TND provides reliable estimates of TCV effectiveness, whereas the cohort design can bias vaccine effectiveness estimates, possibly due to unmeasured confounding effects, such as health-care-seeking behaviours. NCE and NCO approaches are useful tools for identifying such biases. FUNDING: The Bill & Melinda Gates Foundation.