Zahid Hasan Khan

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.

Virulent bacteriophages (phages) can kill bacterial prey, potentially reducing burden of infection. In cholera, a high phage to Vibrio cholerae ratio is associated with mild dehydration, yet the relative importance of this ratio in disease severity remains unclear. We used machine learning to rank select host, microbial, and environmental factors as determinants of dehydration severity in over 600 cholera patients from across Bangladesh. We found the phage:pathogen ratio ranked among the top classifiers for mild dehydration, behind age and location. We advocate that phage predation be included as a key factor in cholera characterization for scientific, clinical and epidemiological applications.

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.

Antibiotic resistance is a significant public health concern and requires coordinated efforts to promote antibiotic stewardship. In rural Bangladesh, informal healthcare providers known as “village doctors” are a primary source of antibiotics for a range of ailments, including pediatric diarrhea. This qualitative study explored the factors influencing antibiotic dispensing practices for pediatric diarrhea among village doctors in the Chattogram district of Bangladesh. In May 2023, we conducted in-depth interviews with 18 village doctors and analyzed the data using thematic analysis approach. The resulting themes were mapped onto the five domains of the Social Ecological Framework (SEF) to identify the multi-level drivers of antibiotic dispensing practices. At the individual level, antibiotic provision for treatment of pediatric diarrhea is influenced by village doctors’ clinical knowledge, training, and beliefs about antibiotics. At the interpersonal level, village doctors often alter their antibiotic dispensing practices based on patient and caregiver demands and influences from pharmaceutical companies. Organizational level factors include financial incentives from medication sales and pharmaceutical companies, resource constraints, diagnostic limitations, and a competitive healthcare landscape. We also identified that cultural expectations for rapid recovery through antibiotics and widespread community access to antibiotics at the community level. Finally, at the policy level, we identified weak regulatory frameworks, inadequate enforcement mechanisms, and healthcare system challenges that position village doctors as essential but unregulated providers. The findings highlight the multi-level drivers for inappropriate antibiotic use. Effective interventions should enhance clinical training, address economic incentives, promote community education, and establish clear regulatory frameworks. Future strategies should consider the interconnected nature of these influences rather than targeting isolated levels.

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.

Diarrheal diseases are a leading cause of morbidity and mortality in children globally, and antibiotics are often inappropriately used in the management of pediatric diarrhea. This study explores how parents’ expectations influence the prescription of antibiotics for pediatric diarrhea in Bangladesh. We used qualitative methods to explore parents’ expectations when bringing their child with diarrhea to hospital and how physicians perceive and manage expectations. We conducted interviews with 36 parents and 18 hospital physicians across three hospitals. Data analysis followed an applied thematic analysis framework. Parents expected a higher quality of care in the hospital setting, including diagnostic testing, medication, and psychosocial support. Most parents did not expect antibiotics as treatment for pediatric diarrhea, yet most parents expressed a belief that antibiotics were superior to other medications. Physicians recognized this parental belief about antibiotic superiority, but some mistakenly assumed parents universally expected antibiotics. Physicians stated that the most common form of managing parents’ expectations is via educational counseling. Physicians’ assumptions that parents expect to receive antibiotics may lead to inappropriate antibiotic prescription and be a source of frustration for both parties. Shared decision-making interventions can assist physicians in exploring and managing parent expectations to promote antibiotic stewardship.

: 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.

Treatment of life-threatening diarrheal illness in rural areas of Bangladesh relies on the training and accessibility of informal health care providers such as village doctors. We found that village doctors located closer to main roads were more likely to be government trained but just as likely to administer intravenous fluids.

Background and Aims: Primary nocturnal enuresis (PNE) is a common pediatric condition characterized by involuntary nighttime bed wetting. Primary monosymptomatic nocturnal enuresis (PMNE) is associated with altered antidiuretic hormone (ADH) secretion and lacks lower urinary tract symptoms. This study aimed to compare serum ADH levels between children with PMNE and a comparison group to explore its potential role in the pathophysiology of PMNE. Methods: This cross‐sectional study included 40 children aged 6–15 years with PMNE and 40 age‐matched children without enuresis (comparison group) attending the Pediatric Nephrology Outpatient Department at the National Institute of Kidney Diseases and Urology (NIKDU) from January 2022 to July 2023. Blood samples and other clinical information along with laboratory investigation are done to ensure inclusion and exclusion criteria. Fasting serum ADH level, a competitive immunoassay was done with the Arg‐ Vasopressin ELISA kit. Relevant clinical and demographic data were analyzed using Student's t ‐test for continuous variables and Chi‐square/Fisher's exact tests for categorical variables. Results: The mean age of participants was 8.82 ± 2.71 years in the PMNE group and 9.01 ± 2.54 years in the comparison group ( p = 0.760). There was no significant association between sex and PMNE ( p = 0.370). Children with PMNE exhibited significantly lower serum ADH levels compared to the comparison group ( p < 0.05). Additionally, children with more frequent enuretic episodes demonstrated a trend of lower ADH levels ( p < 0.05). Conclusion: This study provides evidence of a significant association between decreased diurnal serum ADH levels and PNE in children. These findings contribute to a better understanding of the pathophysiology of PNE and suggest potential avenues for novel treatment strategies, emphasizing the importance of evaluating ADH levels in PNE management.