Background: From May to December 2021, Bangladesh experienced a major surge in the Delta variant of SARS-CoV-2. The earlier rollout of several vaccines offered the opportunity to evaluate vaccine effectiveness against this variant. Methods: A prospective, test-negative case-control study was conducted in five large hospitals in Dhaka between September and December 2021. The subjects were patients of at least 18 years of age who presented themselves for care, suffering COVID-like symptoms of less than 10 days’ duration. The cases had PCR-confirmed infections with SARS-CoV-2, and up to 4 PCR test-negative controls were matched to each case, according to hospital, date of presentation, and age. Vaccine protection was assessed as being the association between the receipt of a complete course of vaccine and the occurrence of SARS-CoV-2 disease, with symptoms beginning at least 14 days after the final vaccine dose. Results: In total, 313 cases were matched to 1196 controls. The genotyping of case isolates revealed 99.6% to be the Delta variant. Receipt of any vaccine was associated with 12% (95% CI: −21 to 37, p = 0.423) protection against all episodes of SARS-CoV-2. Among the three vaccines for which protection was evaluable (Moderna (mRNA-1273); Sinopharm (Vero Cell-Inactivated); Serum Institute of India (ChAdOx1 nCoV-19)), only the Moderna vaccine was associated with significant protection (64%; 95% CI: 10 to 86, p = 0.029). Protection by the receipt of any vaccine against severe disease was 85% (95% CI: 27 to 97, p = 0.019), with protection estimates of 75% to 100% for the three vaccines. Conclusions: Vaccine protection against COVID-19 disease of any severity caused by the Delta variant was modest in magnitude and significant for only one of the three evaluable vaccines. In contrast, protection against severe disease was high in magnitude and consistent for all three vaccines. Because our findings are not in complete accord with evaluations of the same vaccines in more affluent settings, our study underscores the need for country-level COVID-19 vaccine evaluations in developing countries.

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.

In low- and middle-income countries, Shigella is an important cause of diarrheal disease, and infections often occur without clinical symptoms. Asymptomatic individuals may act as reservoirs for ongoing community transmission, but their contribution to the overall burden remains poorly understood. This analysis aimed to generate evidence on asymptomatic and symptomatic Shigella infection in Dhaka, Bangladesh, to enlighten surveillance and prevention strategies. We analyzed data from the hospital-based diarrheal disease surveillance system (DDSS) of icddr,b Dhaka Hospital and asymptomatic participants from the community, covering January to December 2025. Stool or rectal swabs were cultured and serotyped for Shigella species. In 2025, Shigella was detected in 68 (2.5%, 95% CI: 2.0–3.1%) among 2738 diarrheal patients, compared with 51 of 784 asymptomatic community participants (6.5%, 95% CI: 5.0–8.4%) and this difference was significant (p value < 0.001). In both groups, participants aged 5–17 years had the highest positivity (hospital 6.2% and community 12.1%). Positivity was also significantly higher in the community for both males (7.6% vs. 2.8%, p < 0.001) and females (5.3% vs. 2.1%, p = 0.001). S. flexneri was predominant in both populations (64.7% and 58.8%). S. sonnei was more common among hospital patients (29.4% vs. 5.9%), whereas S. boydii was more common among community participants (31.4% vs. 4.4%). Hospital positivity was observed throughout the year, with no clear seasonal peak, whereas community positivity climbed in October and December. Integrated hospital and community surveillance may provide a more complete understanding of Shigella transmission and guide prevention strategies.

Background and Objectives: The morbidity and mortality associated with COVID-19 have burdened worldwide healthcare systems beyond their capacities, forcing them to promptly investigate the virus characteristics and its associated outcomes. This clinical analysis aimed to explore the key factors related to the fatal outcome of severe COVID-19 cases. Materials and Methods: Thirty-five adult severe COVID-19 patients were enrolled from two COVID-19 hospitals in Dhaka, Bangladesh. Clinical manifestation, comorbid conditions, medications, SARS-CoV-2 RT-PCR related cycle threshold (CT) value, hematology, biochemical parameters with SARS-CoV-2 specific IgG and IgM responses at enrollment were compared between the survivors and deceased participants. Results: Total 27 patients survived and 8 patients died within 3 months of disease onset. Deceased patients suffered longer from shortness of breath than the survived (p = 0.049). Among the severe cases, 62% of the deceased patients had multiple comorbid condition compared to 48% of those who survived. Interestingly, the anti-viral was initiated earlier among the deceased patients [median day of 1 (IQR: 0, 1.5) versus 6.5 (IQR: 6.25, 6.75)]. Most of the survivors (55%) received a combination of anticoagulant (p = 0.034). Liver enzymes, creatinine kinase, and procalcitonin were higher among the deceased patients during enrollment. The median CT value among the deceased was significantly lower than the survivors (p = 0.025). A significant difference for initial IgG (p = 0.013) and IgM (p = 0.030) responses was found between the survivor and the deceased groups. Conclusions: The factors including older age, male gender, early onset of respiratory distress, multiple comorbidities, low CT value, and poor antibody response may contribute to the fatal outcome in severe COVID-19 patients. Early initiation of anti-viral and a combination of anticoagulant treatment may prevent or lower the fatality among severe COVID-19 cases.

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.