Taufiqul Islam

Introduction: A cluster randomized trial (CRT) in Bangladesh found that Vi-tetanus toxoid (Vi-TT) vaccine conferred 85% protection to vaccinees at 18 months of follow-up; however, it failed to confer significant herd protection to non-vaccinees. Methods: In the CRT, children aged 9 months to <16 years from 150 clusters received one dose of either Vi-TT or Japanese encephalitis vaccine. To evaluate whether herd protection was evident, we analyzed two years of follow-up data by quartiles of clusters with ascending levels of Vi-TT coverage. Results: The average vaccine coverage across all clusters was 69% among targeted children and 20% in the entire population. Vi-TT provided 83% (95%CI: 74%,89%) total protection among vaccinees, 12% (95%CI: -17%,34%) indirect protection among non-vaccinees, and 53% (95%CI: 40%,63%) overall protection among entire population, irrespective of vaccine coverage. Significant herd protection (47%; 95%CI: 3%,71%) was observed only in the highest quartile of vaccine coverage in the entire population (range 21.5%-26%). No herd protection was evident among targeted children (<16 years), including the highest coverage quartile (72.1%-78.9%), where protection was - 8% (95%CI: -108%,44%). Conclusion: Vaccine herd protection, essential for typhoid conjugate vaccines to achieve high overall protection, was evident only in clusters with higher, albeit still modest, coverage in the entire population. Since even high coverage among children <16 years did not generate significant herd protection, higher vaccine coverage across all age groups, including vaccination of adults, may be necessary for TCVs to confer the combined direct and herd protection required for effective typhoid control. Summary box: What is already known on this topic?: Vi-tetanus toxoid (Vi-TT) vaccine provides high-level protection against typhoid fever in vaccinated children. However, overall analysis of a cluster-randomized trial of Vi-TT given to children under 16 years of age found no evidence of indirect (herd) protection by Vi-TT to unvaccinated individuals. What this study adds: In further analysis of the cluster randomized trial of Vi-TT, significant indirect protection (47%; 95%CI:3%,71%) was observed, but only in clusters with the highest levels of vaccine coverage of the entire population. In contrast, we found no evidence of vaccine herd protection in clusters with the highest levels of vaccine coverage of children, who were targeted by vaccination. How this study might affect research, practice, or policy: Achieving herd protection from typhoid conjugate vaccines (TCVs) may require higher vaccine coverage across the entire population, not only among children. Vaccination strategies that include adults may be necessary to maximize the public health impact of TCVs. These findings have important implications for typhoid control policies in endemic settings.

Background: The dynamics of humoral immune responses following primary and booster COVID-19 vaccinations are crucial to understand in order to optimize vaccination strategies. This study evaluates the magnitude and durability of SARS-CoV-2-specific IgG antibody responses across different vaccines in a large cohort of Bangladeshi adults. Methods: A total of 6300 adults from nine hospitals across eight divisions of Bangladesh were enrolled. Participants received two primary doses of either ChAdOx1 nCoV-19 (Covishield, Serum Institute of India, n = 2855), mRNA-1273 (Moderna, n = 578), BNT162b2 (Pfizer-BioNTech, n = 121), or Vero-cell-inactivated (Sinopharm, n = 2746) vaccines. Booster doses were administered at one-year intervals post-primary vaccination. SARS-CoV-2 spike receptor-binding domain (RBD)-specific IgG antibody responses were measured by ELISA using serum from vaccinees at multiple time points after two primary and two booster doses. Results: A total of 3745 individuals received booster 1 (third dose), with 59% receiving heterologous boosters (a different vaccine regimen than the primary doses). Only 5.5% (n = 347) of participants received a second booster one year after the first booster (among them, 99% received BNT162b2). Our results suggest that heterologous boosters with the mRNA vaccine induced higher IgG levels than homologous boosters for individuals who received primary vaccination with adenovirus vector-based ChAdOx1 nCoV-19 or a Vero-cell-inactivated vaccine. However, in those who initially received the mRNA-based vaccine, both homologous and heterologous boosters produced comparable IgG responses. Among all vaccine types, booster immunization with the Vero-cell-inactivated vaccine induced the lowest antibody responses. Longitudinal analysis demonstrated significantly high IgG levels over the 12 months following the first booster (p < 0.0001); however, IgG levels declined significantly after the second booster dose (fourth dose). Conclusions: Heterologous boosting strategies, particularly those involving mRNA vaccines, elicit stronger and more sustained IgG responses compared to a homologous booster. However, antibody waning after the second booster highlights the need for continued monitoring and potential additional vaccine strategies.

Background: In Bangladesh, cholera treatment focuses on acute watery diarrhea in symptomatic cases at health facilities, though asymptomatic infections are common. Understanding the role of asymptomatic infections in transmission is crucial for designing appropriate control strategies in this setting. Methods: We utilized data from household studies conducted in Dhaka, Bangladesh, during 2006–2018 where a symptomatic confirmed cholera case and their household contacts were followed for 30 days. Vibriocidal antibodies, bacteriological culture, and symptom histories were collected at multiple time points. We used a hidden Markov model to estimate risk of infection from intra-household and extra-household (ie, community and environmental) sources and to quantify relative risk of transmission from symptomatic and asymptomatic infected household contacts. Results: Estimated daily risk of intra-household infection from a symptomatic individual to another household member was 2.6% (95% credible interval [CrI], .4%–5.6%) and from an asymptomatic infected individual to another household member was 1.6% (95% CrI, .2%–4.5%). We found no significant differences in probability of infection from asymptomatic compared to symptomatic individuals (odds ratio, 0.60 [95% CrI, .11–3.23]). We estimated that daily risk of infection from extra-household sources during follow-up was 1.0% (95% CrI, .7%–1.4%). Conclusions: Mitigation measures focused solely on treatment of symptomatic cholera cases may be insufficient to prevent transmission in a household. This supports use of interventions that reduce risk of transmission irrespective of symptoms, such as prophylactic antibiotic treatment for household members, vaccination, and/or providing safe water and hygiene kits following a confirmed household or community case.

Background: The rising incidence and case fatality rates of cholera outbreaks underscore the need for better diagnostic tests for early detection and confirmation of the outbreak to enable rapid responses and obtain reliable surveillance data. We evaluated the Rapid LAMP-based Diagnostic Test (RLDT) for detecting cholera to determine if this test has the potential to fill the gap. Methods: This study included training and evaluation of RLDT in the cholera reference laboratory in Bangladesh. Stool samples collected from suspected cholera patients seeking care at the icddr,b hospital, Dhaka, were tested using cholera RLDT, microbiological culture, Rapid Diagnostic Test (RDT crystal VC O1, O139), and PCR and compared. Results: Out of 205 cases analyzed, 136 (66%) were positive for cholera by RLDT, 131 (64%) by PCR, 92 (45%) by culture, and 90 (44%) by RDT. The RLDT was highly specific, as all the culture positives were positive by RLDT, except 1 (sensitivity of 99%), and could detect all the PCR positives except 2 (sensitivity of 97%). Almost perfect agreement was found between RLDT and PCR (kappa 0.9). Rapid LAMP-based Diagnostic Test being more sensitive than culture and RDT, the agreement was moderate (kappa 0.6 and 0.5, respectively). Rapid Diagnostic Test missed detection of cholera in 11 samples, positive by other tests. The accuracy of RLDT was 100% in detecting cholera from water samples. Conclusions: Rapid LAMP-based Diagnostic Test was specific and sensitive, detecting 21% more cholera-positive cases than culture or RDT. Rapid LAMP-based Diagnostic Test has the potential to improve the rapid detection of cholera in outbreak situations and for surveillance data.

: In low- and middle-income countries, informal healthcare providers are often the first point of contact for pediatric care. The present qualitative study, conducted in Bangladesh, was designed to explore why parents seek pediatric care from informal providers. Through in-depth interviews with 12 parents of children under 5 years of age, key drivers for visiting informal providers were identified, including geographic and financial accessibility, as well as trust and familiarity. Parents expected informal providers to offer them informed and effective treatment but did not have a clear understanding of evidence-based treatment of pediatric diarrhea. Although informal providers may meet families’ immediate needs, they can also undermine formal healthcare visits and follow-ups that are essential to supporting children’s long-term health. The study findings highlight the need for targeted health education to improve parents’ knowledge, awareness, and informed decision-making. Strengthening trust in formal providers and addressing accessibility barriers is essential to improving pediatric health outcomes in low-resource settings.

Background and Aims: Climate variability worsens waterborne diseases like diarrhea, especially in developing countries. This study investigated the link between climate factors and a diarrheal upsurge in Dhaka during May–June 2024. Methods: This cross‐sectional study was conducted in the International Center for Diarrheal Disease Research, Bangladesh (icddr,b). We considered samples from patients and climate data from May 1st to June 30th, 2024, for comprehensive analysis and comparison. We used data from icddr,b Dhaka hospital's 2% surveillance system and climate data from national aeronautics and space administration (NASA) for the same period of Dhaka city. All analyzes were conducted using R statistical software (R‐4.3.2) and a p ‐value of less than 0.05 was considered statistically significant. Results: A total of 737 patients were enrolled during May–June, with 137 cases recorded during the upsurge period from 2% of the surveillance. The most detected pathogens (10% were both vibrio cholerae and Enterotoxigenic Escherichia coli (ETEC). Cholera and also ETEC. V. cholerae was significantly ( p < 0.001) associated with age, dehydration, fever, vomiting, abdominal pain, and water source ( p = 0.003). Temperatures remained unusually high (40°C–45°C) ahead of the upsurge before dropping, coinciding with a surge in diarrhea cases. As temperatures stabilized at 30°C–32°C, cases declined. Rainfall (180 mm) and wind speed (18 km/h) peaked just prior to the upsurge, while humidity rose above 80%, coinciding with an increase in diarrhea cases. Conclusion: This study highlights how climate factors influence diarrheal disease in Dhaka and urges policymakers to prioritize climate resilience and targeted interventions.

: Rural Bangladesh faces challenges of limited health care resources and a shortage of health care professionals. Informal providers, particularly village doctors, fill this void by being a first point of care and a bridge to the formal health care system. This study explores formally trained physicians’ perspectives on village doctors’ role in the health care system. This qualitative study was conducted in southeast Bangladesh and included 12 individual in-depth interviews with physicians. Data were analyzed using applied thematic analysis, focusing on both the contributions and shortcomings of village doctors. Three themes emerged for positive contributions of village doctors: 1) provision of essential services and resources in isolated areas, 2) enhanced accessibility and familiarity with the community, and 3) active involvement in public health education. Five themes emerged related to the shortcomings and negative impacts of village doctors: 1) insufficient education and training, 2) use of inappropriate treatments, 3) inappropriate referrals, 4) misuse and overuse of antibiotics, and 5) prioritization of financial gain. This study sheds light on the complex interplay between formal and informal health care providers, emphasizing both the contributions and shortcomings of village doctors in rural health care settings.

Background: Shigella spp are among the notable causes of global diarrheal disease and death, accounting for 13.2% of deaths in 2016. Antimicrobial resistance complicates shigellosis management. Understanding local disease epidemiology is crucial for developing effective preventive strategies, including vaccine use. Methods: We investigated antimicrobial resistance, risk factors (socioeconomic, behavioral, and water, sanitation and hygiene (WaSH), and clinical characteristics of Shigella diarrhea in Mukuru informal settlement and surrounding villages in Nairobi, Kenya. Patients presenting with diarrhea, fever, or both in treatment centers had stool or rectal swab samples cultured, and bacteria was identified through biochemical and serologic tests. Results: The rate of Shigella isolation among the 4689 individuals presenting with diarrhea was 1.4% across all ages, with a similar isolation rate (1.5%) among children <5 years of age. The majority of the Shigella spp (40 [59.7%]) were Shigella flexneri, and the majority of S flexneri (34 of 40 [85%]) were resistant to trimethoprim-sulfamethoxazole; however, all were sensitive to amoxicillin-clavulanate, ceftazidime, ceftriaxone, and cefpodoxime. The rate of multidrug resistance was higher in Shigella sonnei (13 [48.1%]) than in S flexneri (3 [7.5%]). Shigella positivity was associated with bloody diarrhea, severe/moderate dehydration, coated tongue, and high fever. Consumption of street food was also associated with Shigella diarrhea. Conclusions: Despite low prevalence, shigellosis still poses a significant burden of diarrheal disease, warranting future incidence studies. First-line antibiotics against Shigella remain effective, but intermediate resistance to azithromycin and ciprofloxacin is a concerning trend. Improving household food preparation and handling could potentially reduce Shigella infections.

The provision of health care services in low- and middle-income countries (LMICs) heavily relies on informally trained health care providers, who are responsible for up to 90% of health care interactions in these regions [1]. Bangladesh is particularly reliant on informally trained providers, given the shortage of qualified health care professionals in rural areas [2]. […]