Inadequate sanitation in healthcare facilities: A comprehensive evaluation of toilets in major hospitals in Dhaka, Bangladesh.

BACKGROUND: Lack of access to functional and hygienic toilets in healthcare facilities (HCFs) is a significant public health issue in low- and middle-income countries (LMICs), leading to the transmission of infectious diseases. Globally, there is a lack of studies characterising toilet conditions and estimating user-to-toilet ratios in large urban hospitals in LMICs. We conducted a cross-sectional study in 10-government and two-private hospitals to explore the availability, functionality, cleanliness, and user-to-toilet ratio in Dhaka, Bangladesh. METHODS: From Aug-Dec 2022, we undertook infrastructure assessments of toilets in selected hospitals. We observed all toilets and recorded attributes of intended users, including sex, disability status, patient status (in-patient/out-patient/caregiver) and/or staff (doctor/nurse/cleaner/mixed-gender/shared). Toilet functionality was defined according to criteria used by the WHO/UNICEF Joint-Monitoring Programme in HCFs. Toilet cleanliness was assessed, considering visible feces on any surface, strong fecal odor, presence of flies, sputum, insects, and rodents, and solid waste. RESULTS: Amongst 2875 toilets, 2459 (86%) were observed. Sixty-eight-percent of government hospital toilets and 92% of private hospital toilets were functional. Only 33% of toilets in government hospitals and 56% in private hospitals were clean. A high user-to-toilet ratio was observed in government hospitals' outpatients service (214:1) compared to inpatients service (17:1). User-to-toilet ratio was also high in private hospitals' outpatients service (94:1) compared to inpatients wards (19:1). Only 3% of toilets had bins for menstrual-pad disposal and <1% of toilets had facilities for disabled people. CONCLUSION: A high percentage of unclean toilets coupled with high user-to-toilet ratio hinders the achievement of SDG by 2030 and risks poor infection-control. Increasing the number of usable, clean toilets in proportion to users is crucial. The findings suggest an urgent call for attention to ensure basic sanitation facilities in Dhaka's HCFs. The policy makers should allocate resources for adequate toilets, maintenance staff, cleanliness, along with strong leadership of the hospital administrators.

Surveillance of Bacterial Load and Multidrug-Resistant Bacteria on Surfaces of Public Restrooms.

Public restrooms are often a hub of microbial contamination and the examination of bacterial contamination in these facilities can serve as an important indicator of the transmission of infectious diseases. This study was conducted to determine the prevalence of bacterial contamination in public restrooms based on the economic class of the building. Samples were collected from various spots in 32 restrooms found in 10 shopping malls, classifying them into two categories: upper-end restrooms and lower-end restrooms. The findings showed that the level of contamination was higher in the lower-end restrooms, with the seat being the most contaminated area. The most dominant Gram-positive bacteria were of the coagulase-negative staphylococci species, making up 86% of the identified Gram-positive isolates. The most dominant Gram-negative bacteria identified were Klebsiella pneumoniae (K. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa). The antibiotic sensitivity test results revealed the presence of multidrug-resistant bacteria among the Gram-positive and negative isolates, including Staphylococcus haemolyticus (S. haemolyticus), Staphylococcus kloosii (S. kloosii), Acinetobacter baumanii (A. baumanii), and P. aeruginosa. In conclusion, the study underscores the significance of monitoring bacterial contamination in public restrooms and the need for measures to reduce the spread of infectious diseases. Further research is crucial to gain a complete understanding of the bacterial contamination in public restrooms and their resistance patterns, to ensure the safety and health of the public. The implementation of improved cleaning practices and hands-free designs in addition to the installation of antimicrobial surfaces in restrooms can help reduce the risk of cross-contamination and prevent the spread of diseases.

The reactive cholera vaccination campaign in urban Dhaka in 2022: experience, lessons learned and future directions.

Introduction: An upsurge of diarrheal cases occurred in Dhaka, Bangladesh, with approximately 30% of the cases being identified as cholera in 2022. To combat this situation, a reactive Oral Cholera Vaccination campaign was organized in five highly cholera-affected areas of Dhaka city. The paper is a descriptive tale of experience gathering, organization and implementation of reactive oral cholera vaccination campaign. Study design: This is a descriptive report of a reactive oral cholera vaccination campaign. Methods: Population density maps were generated using GIS technology before launching the campaign. The target population comprised individuals aged over one year, excluding pregnant women, totaling 2,374,976 people residing in above mentioned areas. The campaign utilized Euvichol-Plus, an OCV with adherence to the necessary cold chain requirements. Total 700 teams, each consisting of six members, were deployed across the five zones. The campaign was conducted in two rounds, where first round took place in June-July 2022, followed by second round in August 2022. During the campaign, data on adverse events following immunization (AEFI) was collected. Expert teams from various government and non-government organizations monitored regularly and ensured the campaign's success. Results: The first round achieved a coverage rate of 99%, whereas in the second round, 86.3% of individuals among the first dose recipients. During the campaigns, a total of 57 AEFIs were reported. Conclusions: This campaign serves as a model for a multispectral approach in combating cholera epidemics, highlighting the collaborative efforts of policymakers, health authorities, local communities, and health partners.

CAPTURA Regional Workshop Proceedings (28-30 June 2022, Virtual).

In response to the global threat of antimicrobial resistance (AMR), the Capturing Data on Antimicrobial Resistance Patterns and Trends in Use in Regions of Asia (CAPTURA) project worked with microbiology laboratories, pharmacies, and local governments in South Asia and Southeast Asia to expand the volume of historical and current data available on AMR and antimicrobial use and to identify gaps in data and areas for quality improvement. When the CAPTURA project completed its country-level engagement in the first half of 2022, the consortium brought together local, regional, and global AMR stakeholders for a virtual regional workshop to review data outputs from the project and share strategies to inform national and regional efforts to combat AMR. This paper summarizes the main topics presented in the workshop held from 28 to 30 June 2022. As such, it highlights lessons learned from the project and strategies to fight AMR. Although CAPTURA has been invaluable to countries and information from the project is already being used, barriers concerning data quality and sharing remain. Regional-level initiatives should continue to build on the momentum gained from the CAPTURA project in supporting national-level surveillance and data quality improvements to inform critical decisions around planning, policies, and clinical care. Project findings have highlighted that issues with antimicrobial resistance and use are wide ranging across countries. Going forward, building on the current foundations and tailoring approaches to meet local needs and capacities will be fundamental in combatting AMR.

Antimicrobial Resistance Surveillance Methods in Bangladesh: Present and Way Forward.

The Institute of Epidemiology, Disease Control and Research (IEDCR) conducts active, case-based national antimicrobial resistance (AMR) surveillance in Bangladesh. The Capturing Data on Antimicrobial Resistance Patterns and Trends in Use in Regions of Asia (CAPTURA) project accessed aggregated retrospective data from non-IEDCR study sites and 9 IEDCR sites to understand the pattern and extent of AMR and to use analyzed data to guide ongoing and future national AMR surveillance in both public and private laboratories. Record-keeping practices, data completeness, quality control, and antimicrobial susceptibility test practices were investigated in all laboratories participating in case-based IEDCR surveillance and laboratory-based CAPTURA sites. All 9 IEDCR laboratories recorded detailed case-based data (n = 16 816) in electronic format for a priority subset of processed laboratory samples. In contrast, most CAPTURA sites (n = 18/33 [54.5%]) used handwritten registers to store data. The CAPTURA sites were characterized by fewer recorded variables (such as patient demographics, clinical history, and laboratory findings) with 1 020 197 individual data, less integration of patient records with the laboratory information system, and nonuniform practice of data recording; however, data were collected from all available clinical samples. The analyses conducted on AMR data collected by IEDCR and CAPTURA in Bangladesh provide current data collection status and highlight opportunities to improve ongoing data collection to strengthen current AMR surveillance system initiatives. We recommend a tailored approach to conduct AMR surveillance in high-burden, resource-limited settings.

A snap-shot of a diarrheal epidemic in Dhaka due to enterotoxigenic Escherichia coli and Vibrio cholerae O1 in 2022.

Background: Enterotoxigenic Escherichia coli (ETEC) and Vibrio cholerae O1 are most common bacterial causes of diarrheal diseases in Bangladesh. This analysis projected distribution of ETEC and V. cholerae O1 among diarrheal patients of icddr,b, Dhaka hospital in two diarrheal peaks of 2022. Methodology: Under the 2% systematic surveillance system, stool samples collected from diarrheal patients of icddr,b hospital were cultured and diagnostic testing was done for ETEC and V. cholerae O1. Comparison of positive cases was done between first peak (March-April) and second peak (October-November) in 2022. Results: A total of 2,937 stool specimens were tested of which 12% were ETEC and 20% were V. cholerae O1. About 40% of the severe dehydration cases were infected with V. cholerae O1. Predominant ETEC enterotoxin type was 'LT/ST' (41%). The LT enterotoxin significantly increased from 13% to 28% in the second peak (p = 0.015). The predominant colonization factors (CFs) on ETEC were CS5 + CS6 (23%), followed by CS6 (15%). CF-positive isolates was significantly higher in the second peak (36%) than in the first peak (22%) (p = 0.043). Total 14% cases were co-infected with ETEC and V. cholerae O1. Significant differences in the distribution of enterotoxin types were observed (p = 0.029) among the co-infection cases. Conclusion: Changing patterns of enterotoxin and CFs observed in ETEC pathogens should be taken into consideration for ETEC vaccine development. Considering cholera and ETEC biannual trends in causing diarrheal epidemics and outbreaks, emphasizes the need for thoughts on combination vaccine strategies for preventing acute watery diarrhea due to the two major bacterial pathogens.

Implementation and Delivery of Oral Cholera Vaccination Campaigns in Humanitarian Crisis Settings among Rohingya Myanmar nationals in Cox's Bazar, Bangladesh.

BACKGROUND: Over 700,000 Myanmar nationals known as the 'Rohingyas' fled into Cox's Bazar, Bangladesh, in late 2017. Due to this huge displacement into unhygienic areas, these people became vulnerable to communicable diseases including cholera. Assessing the risk, the Government of Bangladesh (GoB), with the help of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) and other international partners, decided to take preventive measures, one of which is the execution of oral cholera vaccination (OCV) campaigns. This paper describes the implementation and delivery of OCV campaigns during humanitarian crises in Bangladesh. METHODS: Seven rounds of OCV campaigns were conducted between October 2017 and December 2021. The OCV campaigns were conducted by applying different strategies. RESULTS: Approximately 900,000 Rohingya Myanmar nationals (RMNs) and the host population (amounting to 528,297) received OCV across seven campaigns. In total, 4,661,187 doses of OCVs were administered, which included 765,499 doses for RMNs, and 895,688 doses for the host community. The vaccine was well accepted, and as a result, a high level of coverage was achieved, ranging from 87% to 108% in different campaigns. CONCLUSIONS: After successful pre-emptive campaigns in Cox's Bazar humanitarian camps, no cholera outbreaks were detected either in the RMN or host communities.

Uptake of Influenza Vaccine and Factors Associated with Influenza Vaccination among Healthcare Workers in Tertiary Care Hospitals in Bangladesh: A Multicenter Cross-Sectional Study.

Influenza, highly contagious in hospital settings, imposes a substantial disease burden globally, and influenza vaccination is critical for healthcare workers (HCWs) to prevent this illness. This study assessed influenza vaccine uptake, including its associated factors among HCWs of tertiary care hospitals in Bangladesh. Between September and December 2020, this multicenter study included 2046 HCWs from 11 hospitals. Face-to-face interviews were conducted using a semi-structured questionnaire to collect data from physicians, nurses, and cleaning and administrative staff for the survey. Only 13.8% (283/2046) of HCWs received the influenza vaccine, of which the majority (76.7%, 217/283) received it for free from the hospital. Nurses had the highest (20.0%, 187/934) influenza vaccine coverage, followed by physicians at 13.5% (71/526), whereas cleaning staff had the lowest at 6.0% (19/318). Among unvaccinated HCWs, the desire to get vaccinated was high (86.2%), with half of the respondents even being willing to pay for it. The HCWs who were aware of the influenza vaccine were over five times more likely to get the vaccine (OR 5.63; 95% CI: 1.04, 1.88) compared to those who were not. HCWs in Bangladesh were vaccinated against influenza at a very low rate. Free and mandatory influenza vaccination programs should be initiated to optimize vaccine coverage among HCWs.

The effect of vitamin D supplementation on pain: an analysis of data from the D-Health randomised controlled trial.

Observational studies suggest that 25-hydroxy vitamin D (25(OH)D) concentration is inversely associated with pain. However, findings from intervention trials are inconsistent. We assessed the effect of vitamin D supplementation on pain using data from a large, double-blind, population-based, placebo-controlled trial (the D-Health Trial). 21 315 participants (aged 60-84 years) were randomly assigned to a monthly dose of 60 000 IU vitamin D3 or matching placebo. Pain was measured using the six-item Pain Impact Questionnaire (PIQ-6), administered 1, 2 and 5 years after enrolment. We used regression models (linear for continuous PIQ-6 score and log-binomial for binary categorisations of the score, namely 'some or more pain impact' and 'presence of any bodily pain') to estimate the effect of vitamin D on pain. We included 20 423 participants who completed ≥1 PIQ-6. In blood samples collected from 3943 randomly selected participants (∼800 per year), the mean (sd) 25(OH)D concentrations were 77 (sd 25) and 115 (sd 30) nmol/l in the placebo and vitamin D groups, respectively. Most (76 %) participants were predicted to have 25(OH)D concentration >50 nmol/l at baseline. The mean PIQ-6 was similar in all surveys (∼50·4). The adjusted mean difference in PIQ-6 score (vitamin D cf placebo) was 0·02 (95 % CI (-0·20, 0·25)). The proportion of participants with some or more pain impact and with the presence of bodily pain was also similar between groups (both prevalence ratios 1·01, 95 % CI (0·99, 1·03)). In conclusion, supplementation with 60 000 IU of vitamin D3/month had negligible effect on bodily pain.

Infection prevention and control in tertiary care hospitals of Bangladesh: results from WHO infection prevention and control assessment framework (IPCAF).

INTRODUCTION: Infection prevention and control (IPC) in healthcare settings is imperative for the safety of patients as well as healthcare providers. To measure current IPC activities, resources, and gaps at the facility level, WHO has developed the Infection Prevention and Control Assessment Framework (IPCAF). This study aimed to assess the existing IPC level of selected tertiary care hospitals in Bangladesh during the COVID-19 pandemic using IPCAF to explore their strengths and deficits. METHODS: Between September and December 2020, we assessed 11 tertiary-care hospitals across Bangladesh. We collected the information from IPC focal person and/or hospital administrator from each hospital using the IPCAF assessment tool.. The score was calculated based on eight core components and was used to categorize the hospitals into four distinct IPC levels- Inadequate, Basic, Intermediate, and Advanced. Key performance metrics were summarized within and between hospitals. RESULTS: The overall median IPCAF score was 355.0 (IQR: 252.5-397.5) out of 800. The majority (73%) of hospitals scored as 'Basic' IPC level, while only 18% of hospitals were categorized as 'Intermediate'. Most hospitals had IPC guidelines as well as environments, materials and equipments. Although 64% of hospitals had IPC orientation and training program for new employees, only 30% of hospitals had regular IPC training program for the staff. None of the hospitals had an IPC surveillance system with standard surveillance case definitions to track HAIs. Around 90% of hospitals did not have an active IPC monitoring and audit system. Half of the hospitals had inadequate staffing considering the workload. Bed occupancy of one patient per bed in all units was found in 55% of hospitals. About 73% of hospitals had functional hand hygiene stations, but sufficient toilets were available in only 37% of hospitals. CONCLUSION: The majority of sampled tertiary care hospitals demonstrate inadequate IPC level to ensure the safety of healthcare workers, patients, and visitors. Quality improvement programs and feedback mechanisms should be implemented to strengthen all IPC core components, particularly IPC surveillance, monitoring, education, and training, to improve healthcare safety and resilience.

In-person training on COVID-19 case management and infection prevention and control: Evaluation of healthcare professionals in Bangladesh.

BACKGROUND: As COVID-19 was declared a global pandemic, the major focus of healthcare organizations shifted towards preparing healthcare systems to handle the inevitable COVID-19 burden at different phases and levels. A series of in-person training programs were operated in collaboration with government and partner organizations for the healthcare workers (HCW) of Bangladesh. This study aimed to assess the knowledge of HCWs regarding SARS-CoV-2 infection, their case management, infection prevention and control to fight against the ongoing pandemic. METHODS: As a part of the National Preparedness and Response Plan for COVID-19 in Bangladesh, the training program was conducted at four district-level hospitals and one specialized hospital in Bangladesh from July 1, 2020 to June 30, 2021. A total of 755 HCWs participated in the training sessions. Among them, 357 (47%) were enrolled for the evaluation upon completion of the data, collected from one district hospital (Feni) and one specialized hospital (National Institute of Mental Health). RESULTS: The mean percentage of pre-test and post-test scores of all the participants were found to be 57% (95% CI 8.34-8.91; p 0.01) and 65% (95% CI 9.56-10.15; p <0.001) respectively. The difference of score (mean) between the groups was significant (p<0.001). After categorizing participants' knowledge levels as poor, average and fair, doctors' group has shown to have significant enhancement from level of average to fair compared to that of the nurses. Factors associated with knowledge augmentation of doctors were working in primary health care centers (aOR: 4.22; 95% CI: 1.80, 9.88), job experience less than 5 years (aOR: 4.10; 95% CI: 1.01, 16.63) and experience in caring of family member with COVID-19 morbidity (aOR: 2.06; 95% CI: 1.03, 4.10), after adjusting for relevant covariates such as age, sex and prior COVID-19 illness. CONCLUSION: Considering the series of waves of COVID-19 pandemic with newer variants, the present paper underscores the importance of implementing the structured in-person training program on case management, infection prevention and control for the HCWs that may help for successful readiness prior to future pandemics that may further help to minimize the pandemic related fatal consequences.

Rationale and guidance for strengthening infection prevention and control measures and antimicrobial stewardship programs in Bangladesh: a study protocol.

BACKGROUND: Hospital-acquired infections (HAIs) and antimicrobial resistance (AMR) are major global health challenges. Drug-resistant infectious diseases continue to rise in developing countries, driven by shortfalls in infection control measures, antibiotic misuse, and scarcity of reliable diagnostics. These escalating global challenges have highlighted the importance of strengthening fundamental infection prevention and control (IPC) measures and implementing effective antimicrobial stewardship programs (ASP). This study aims to present a framework for enhancing IPC measures and ASP efforts to reduce the HAI and AMR burden in Bangladesh. METHODS: This implementation approach will employ a mixed-methods strategy, combining both quantitative and qualitative data from 12 tertiary hospitals in Bangladesh. A baseline assessment will be conducted using the Infection Prevention and Control Assessment Framework (IPCAF) developed by the WHO. We will record IPC practices through direct observations of hand hygiene, personal protective equipment (PPE) utilization, and hospital ward IPC infrastructure. Additionally, data on healthcare providers' knowledge, attitudes, and practices regarding IPC and antibiotic prescribing will be collected using both structured questionnaires and qualitative interviews. We will also assist the hospital leadership with establishing and/or strengthening IPC and ASP committees. Based on baseline assessments of each healthcare facility, tailored interventions and quality improvement projects will be designed and implemented. An end-line assessment will also be conducted after 12 months of intervention using the same assessment tools. The findings will be compared with the baseline to determine changes in IPC and antibiotic stewardship practices. DISCUSSION: Comprehensive assessments of healthcare facilities in low-resource settings are crucial for strengthening IPC measures and ASP activities,. This approach to assessing existing IPC and ASP activities will provide policy-relevant data for addressing current shortfalls. Moreover, this framework proposes identifying institutionally-tailored solutions, which will ensure that response activities are appropriately contextualized, aligned with stakeholder priorities, and offer sustainable solutions. CONCLUSION: Findings from this study can guide the design and implementation of feasible and sustainable interventions in resource-constrained healthcare settings to address gaps in existing IPC and ASP activities. Therefore, this protocol will be applicable across a broad range of settings to improve IPC and ASP and reduce the burden of hospital-acquired infections and AMR.

Pattern of Antibiotic Use among Hospitalized Patients according to WHO Access, Watch, Reserve (AWaRe) Classification: Findings from a Point Prevalence Survey in Bangladesh.

For supporting antibiotic stewardship interventions, the World Health Organization (WHO) classified antibiotics through the AWaRe (Access, Watch, and Reserve) classification. Inappropriate use of antimicrobials among hospital-admitted patients exposes them to the vulnerability of developing resistant organisms which are difficult to treat. We aimed to describe the proportion of antibiotic use based on the WHO AWaRe classification in tertiary and secondary level hospitals in Bangladesh. A point prevalence survey (PPS) was conducted adapting the WHO PPS design in inpatients departments in 2021. Among the 1417 enrolled patients, 52% were female and 63% were from the 15-64 years age group. Nearly 78% of patients received at least one antibiotic during the survey period. Third-generation cephalosporins (44.6%), penicillins (12.3%), imidazoles (11.8%), aminoglycosides (7.2%), and macrolides (5.8%) were documented as highly used antibiotics. Overall, 64.0% of Watch, 35.6% of Access, and 0.1% of Reserve group antibiotics were used for treatment. The use of Watch group antibiotics was high in medicine wards (78.7%) and overall high use of Watch antibiotics was observed at secondary hospitals (71.5%) compared to tertiary hospitals (60.2%) (p-value of 0.000). Our PPS findings underscore the need for an urgent nationwide antibiotic stewardship program for physicians including the development and implementation of local guidelines and in-service training on antibiotic use.

Hepatitis B Vaccination Coverage among Bangladeshi Healthcare Workers: Findings from Tertiary Care Hospitals.

Healthcare workers (HCWs) are at a four-fold higher risk of being infected with the hepatitis B virus in hospital settings. This study investigated the hepatitis B vaccination coverage among Bangladeshi HCWs in selected tertiary care hospitals. Between September 2020 to January 2021, a multicenter cross-sectional study was conducted in 11 hospitals across Bangladesh. Participants included physicians, nurses, cleaners, and administrative staff. A semi-structured questionnaire was used to collect data through face-to-face interviews. Descriptive and multivariate statistics were used to analyze the data. The overall hepatitis B vaccination coverage was 66.6% (1363/2046) among HCWs, with cleaning staff having the lowest at 38.8%. Among the unvaccinated, 89.2% of HCWs desired to receive the free vaccine in the near future. In the last year, over one-fourth of staff (27.9%) had at least one history of needlestick injury. Only 9.8% HCWs were found to have attended training on hepatitis B virus prevention and management in the previous two years. Multivariate analysis revealed that physicians (AOR: 7.13, 95% CI: 4.94-10.30) and nurses (AOR: 6.00, 95% CI: 4.09-8.81) were more likely to be vaccinated against hepatitis B than cleaners and administrative staff. Low uptake of hepatitis B vaccination among HCWs suggests policies that require vaccination are needed to achieve optimum vaccine coverage.

Assessment of standard precaution related to infection prevention readiness of healthcare facilities in Bangladesh: Findings from a national cross-sectional survey.

Background: Baseline assessment of standard precaution relating to infection prevention and control (IPC) preparedness to fight health crisis within healthcare facilities at different levels and its associated factors in Bangladesh remains unknown. Methods: We analyzed the nationally representative Bangladesh health facility survey (BHFS) data conducted by the Ministry of Health and Family Welfare (MoHFW) during July-October 2017. We used the World Health Organization (WHO) Service Availability and Readiness Assessment (SARA) manual to determine the standard precautions related to the IPC readiness index. Using a conceptual framework and multivariable linear regression, we identified the factors associated with the readiness index. Results: We analyzed data for 1,524 surveyed healthcare facilities. On average, only 44% of the standard precaution elements were available in all facilities. Essential elements, such as guidelines for standard precautions (30%), hand-washing soap (29%), and pedal bins (38%), were not readily available in all facilities. The tuberculosis service area was least prepared, with 85% of elements required for standard precaution deficient in all facilities. Significantly lower readiness indexes were observed in the rural healthcare facilities (mean difference, -13.2), healthcare facilities administered by the MoHFW (mean difference, -7.8), and private facilities (mean difference, -10.1) compared to corresponding reference categories. Conclusions: Our study revealed a severe lack of standard precaution elements in most healthcare facilities, particularly in rural health centers. These data can provide a baseline from which to measure improvement in infection prevention and control (IPC) in these facilities and to identify areas of gaps for targeted interventions to improve IPC strategies that can improve the Bangladesh health system.

Acute Respiratory Tract Infection and 25-Hydroxyvitamin D Concentration: A Systematic Review and Meta-Analysis.

Observational studies and randomised controlled studies suggest that vitamin D plays a role in the prevention of acute respiratory tract infection (ARTI); however, findings are inconsistent and the optimal serum 25-hydroxyvitamin D (25(OH)D) concentration remains unclear. To review the link between 25(OH)D concentration and ARTI, we searched PubMed and EMBASE databases to identify observational studies reporting the association between 25(OH)D concentration and risk or severity of ARTI. We used random-effects meta-analysis to pool findings across studies. Twenty-four studies were included in the review, 14 were included in the meta-analysis of ARTI risk and five in the meta-analysis of severity. Serum 25(OH)D concentration was inversely associated with risk and severity of ARTI; pooled odds ratios (95% confidence interval) were 1.83 (1.42-2.37) and 2.46 (1.65-3.66), respectively, comparing the lowest with the highest 25(OH)D category. For each 10 nmol/L decrease in 25(OH)D concentration, the odds of ARTI increased by 1.02 (0.97-1.07). This was a non-linear trend, with the sharpest increase in risk of ARTI occurring at 25(OH)D concentration < 37.5 nmol/L. In conclusion, there is an inverse non-linear association between 25(OH)D concentration and ARTI.