Vitamin D plays a crucial role in modulating the innate immune response by interacting with its intracellular receptor, VDR. In this review, we address vitamin D/VDR signaling and how it contributes to the regulation of intestinal and respiratory microbiota. We additionally review some components of the innate immune system, such as the barrier function of the pulmonary and intestinal epithelial membranes and secretion of mucus, with their respective modulation by vitamin D. We also explore the mechanisms by which this vitamin D/VDR signaling mounts an antimicrobial response through the transduction of microbial signals and the production of antimicrobial peptides that constitute one of the body’s first lines of defense against pathogens. Additionally, we highlight the role of vitamin D in clinical diseases, namely inflammatory bowel disease and acute respiratory distress syndrome, where excessive inflammatory responses and dysbiosis are hallmarks. Increasing evidence suggests that vitamin D supplementation may have potentially beneficial effects on those diseases.

Background The implementation of a global COVID-19 vaccination campaign has been one of the most effective interventions in controlling the pandemic. However, vaccine hesitancy remains a major public health challenge, extending to COVID-19 vaccines. This cross-sectional study aimed to assess attitudes toward COVID-19 vaccination and willingness to participate in clinical trials among Saudi university affiliates. Methods An anonymous online questionnaire was distributed between June 2021 and June 2022 to affiliates of four major universities in Riyadh, Saudi Arabia. Attitudes toward vaccination were assessed using the 12-item Vaccination Attitudes Examination (VAX) scale, while attitudes toward clinical trial participation were evaluated through statements rated on a 5-point Likert scale. Statistical analyses were conducted to determine associations between vaccine acceptance, clinical trial participation, and demographic factors. Results A total of 365 respondents participated in the study. The majority were healthcare students, with most in their fourth academic year. Overall, 50.4% of the study sample exhibited vaccine and clinical trial hesitancy. Females exhibited significantly higher vaccine acceptance than males (P = 0.013), though hesitancy rates were only borderline significant between genders (P = 0.063). Healthcare students had significantly higher vaccine acceptance (P < 0.0001) and greater willingness to participate in clinical trials (P < 0.0001) compared to students from science and humanities disciplines. While most participants believed in vaccine safety and effectiveness, many expressed hesitancy regarding the motivations of pharmaceutical companies. Although attitudes toward clinical trials were generally favorable, only 37.8% expressed willingness to participate, and this figure dropped to 32.9% for COVID-19 vaccine trials. Vaccine acceptors were significantly more likely to be willing to participate in clinical trials (P < 0.0001). Conclusions Understanding university students' perspectives on vaccination and clinical trials can help shape targeted public health campaigns to address vaccine hesitancy. Future research is needed to explore determinants of vaccine hesitancy and barriers to clinical trial participation in this population.

The COVID-19 pandemic has necessitated novel approaches to influence public behavior. While “nudging” has gained prominence in Western contexts, its perception and effectiveness in the Arab world remain understudied. This study aimed to investigate the approval of COVID-19-related nudges across four Arab countries and explore associated sociodemographic factors. A cross-sectional study was conducted from November 2020 to January 2022, involving 698 participants from Egypt, Lebanon, Saudi Arabia, and the United Arab Emirates. Participants were presented with eight hypothetical COVID-19-related nudges categorized according to distinct behavioral mechanisms: choice architecture (e.g., floor markers, prominent placement of fruits and vegetables), information disclosure (publicly sharing infection causes), moral appeals (letters from elderly urging compliance), social norm enforcement (public shaming of violators and use of spoilers on billboards), and surveillance-based interventions (GPS tracking of quarantined individuals). Approval rates varied widely (50%–95%). Less intrusive nudges received the highest support: supermarket floor markers (95.4%), prominent display of fruits and vegetables (88.8%), park area divisions (82.0%), infection cause disclosure (86.5%), and elderly letters urging compliance (84.1%). Approval was lower for more intrusive measures, including billboard spoilers (52.0%) and public shaming of curfew violators (49.9%). GPS tracking, the most intrusive intervention, received intermediate approval (72.8%). Higher COVID-19 concern was significantly associated with greater approval of nudges (p < 0.001), with age, gender, and family COVID-19 status also influencing approval rates. These findings demonstrate generally positive attitudes towards COVID-19-related nudges among university affiliates in four Arab countries, with clear variations according to nudge type, intrusiveness, and sociodemographic characteristics. While the results offer valuable insights for culturally tailored behavioral interventions in the Arab world, they reflect a university setting and may not be generalizable to the broader public.