Mesenchymal stem cells (MSCs) play an important role in developing bone tissue engineered constructs due to their osteogenic and chondrogenic differentiation potential. MSC-based tissue engineered constructs are generally considered a safe procedure, however, the long-term results obtained up to now are far from satisfactory. The main causes of these therapeutic limitations are inefficient homing, engraftment, and directional differentiation. Flavonoids are a secondary metabolite, widely existed in nature and have many biological activities. For a long time, researchers have confirmed the anti-osteoporosis effect of flavonoids through in vitro cell experiments, animal studies. In recent years the regulatory effects of flavonoids on mesenchymal stem cells (MSCs) differentiation have been received increasingly attention. Recent studies revealed flavonoids possess the ability to modulate self-renewal and differentiation potential of MSCs. In order to facilitate further research on MSCs osteogenic differentiation of flavonoids, we surveyed the literature published on the use of flavonoids in osteogenic differentiation of MSCs, and summarized their pharmacological activities as well as the underlying mechanisms, aimed to explore their promising therapeutic application in bone disorders and bone tissue engineered constructs.

Purpose Effective public health (PH) response to emerging pathogens requires effective information systems integrating surveillance data from multiple sources. For laboratories, data entry of multiple variables both at pre-analytical steps and again in laboratory information systems (LIS) is time-consuming and difficult to implement in a resource-limited setting and negatively affects the timeliness of the surveillance system. We set up a simple harmonized laboratory query that summarized 22 public-health relevant scenarios and variables, reduced to a two-digit code. Methods & Materials Information data specialists were mobilized to integrate data from the 108 different LIS using the harmonized query, which provided timely access to COVID-19 testing indications, volumes, and positivity rates stratified by age, health region, clinical settings, outbreak context or Health-Care worker status. The information system allowed to develop multiple indicators for a better understanding of the pandemic and the COVID-19 transmission in population subgroups. Results Dashboards were available for public health and infection prevention and control officers in their location. Multiple stakeholders were able to interpret real-time data for more than 40 000 different qPCR tests every day. The data allowed to adjust prescription practice and promote optimal usage and plan contingencies within Quebec's qPCR lab capacities. It also served as the basis to monitor community transmission through test positivity rate in various settings. The coding system also allowed labs to easily implement sample triage, which reduced turnaround time to less than 24h for most samples. Starting May 2021, public health authorities add monitoring of the positive predictive value of rapid antigen test used at the community level to support evidence-based public health decisions about the best possible use of those assays. Conclusion This simple scenario-based coding system allowed timely PH and management of both sampling and processing priorities which proved most useful during surge periods. Quebec Public Health Authorities were better able to target preventive actions and to plan outreach screening activities in subpopulations, neighbourhoods, and communities, while modulating clinical criteria to get access to testing and allowing laboratories to better triage samples.

Antibiotic overprescribing is one of the main drivers of the global and growing problem of antibiotic resistance, especially in primary care and for respiratory tract infections (RTIs). RTIs are the most common reason for patients to consult out-of-hours (OOH) primary care. The COVID-19 pandemic has changed the way general practitioners (GPs) work, both during office hours and OOH. In Belgian OOH primary care, remote consultations with the possibility of issuing prescriptions and telephone triage were implemented. We aimed to describe the impact of COVID-19 on GPs antibiotic prescribing during OOH primary care. In an observational study, using routinely collected health data from GP cooperatives (GPCs) in Flanders, we analyzed GPs antibiotic prescriptions in 2019 (10 GPCs) and 2020 (20 GPCs) during OOH consultations (telephone and face-to-face). We used autoregressive integrated moving average (ARIMA) modeling to identify any changes after lockdowns were implemented. In total, 388,293 contacts and 268,430 prescriptions were analyzed in detail. The number of antibiotic prescriptions per weekend, per 100,000 population was 11.47 (95% CI: 9.08C13.87) or 42.9% lower after compared to before the implementation of lockdown among all contacts. For antibiotic prescribing per contact, we found a decrease of 12.2 percentage points (95% CI: 10.6C13.7) or 56.5% among all contacts and of 5.3 percentage points (95% CI: 3.7C6.9) or 23.2% for face-to-face contacts only. The decrease in the number of prescriptions was more pronounced for cases with respiratory symptoms that corresponded with symptoms of COVID-19 and for antibiotics that are frequently prescribed for RTIs, such as amoxicillin (a decrease of 64.9%) and amoxicillin/clavulanate (a decrease of 38.1%) but did not appear for others such as nitrofurantoin. The implementation of COVID-19 lockdown measures coincided with an unprecedented drop in the number of antibiotic prescriptions, which can be explained by a decrease in face-to-face patient contacts, as well as a lower number of antibiotics prescriptions per face-to-face patient contact. The decrease was seen for antibiotics used for RTIs but not for nitrofurantoin, the first-choice antibiotic for urinary tract infections.

Background: Recent strides in computational structural biology have opened up an opportunity to understand previously uncharacterised proteins. The under-representation of transmembrane proteins in the Protein Data Bank highlights the need to apply new and advanced bioinformatics methods to shed light on their structure and function. This study focuses on a family of transmembrane proteins containing the Pfam domain PF09335 ('SNARE_ASSOC'/ VTT /Tvp38). One prominent member, Tmem41b, has been shown to be involved in early stages of autophagosome formation and is vital in mouse embryonic development as well as being identified as a viral host factor of SARS-CoV-2. Methods: We used evolutionary covariance-derived information to construct and validate ab initio models, make domain boundary predictions and infer local structural features. Results: The results from the structural bioinformatics analysis of Tmem41b and its homologues showed that they contain a tandem repeat that is clearly visible in evolutionary covariance data but much less so by sequence analysis. Furthermore, cross-referencing of other prediction data with covariance analysis showed that the internal repeat features two-fold rotational symmetry. Ab initio modelling of Tmem41b and homologues reinforces these structural predictions. Local structural features predicted to be present in Tmem41b were also present in Cl (-)/H (+ )antiporters. Conclusions: The results of this study strongly point to Tmem41b and its homologues being transporters for an as-yet uncharacterised substrate and possibly using H (+) antiporter activity as its mechanism for transport.

Objective: Early detection of mortality risk is important in patients diagnosed with of coronavirus disease 2019 (COVID-19). Therefore, we aimed to evaluate the predictive value of different clinical and laboratory parameters in disease severity and mortality in patients with COVID-19. Materials and Methods: Patients admitted to hospital with a diagnosis of COVID-19 were evaluated retrospectively. The patients admission date, discharge date, intensive care transfer/ death date, contact history, smoking, symptoms at the time admission, vital markers at admission, and laboratory parameters were recorded. Results: The study included a total of 347 patients, of whom 168 (48.4%) were female. The mean age of the patients was 59.6916.87 (14-97) years, while 40.9% (n=142) were aged over 65 years. Overall, 10.1% (n=35) of the patients required transfer to an intensive care unit and 8.4% (n=29) were deceased. When clinical parameters were evaluated at the time of admission, oxygen saturation was found to be lower in the group that died (79.516.95), compared to the survivors (88.786.11) (p<0.001). Additionally, male gender (p=0.05), advanced age (p<0.001), positive PCR result (p=0.036), congestive heart failure (p=0.044), severe COVID-19 involvement on thorax CT (p<0.001), and presence of at least one comorbidity (p=0.003) were observed at a higher rate in the mortality group. In the multivariate analyses, increased values of the NLR (HR: 1.04, 95% CI: 1.00-1.08), creatinine (OR: 1.37, 95% CI: 1.13-1.66), CRP (=-0.18, OR: 0.98, 95% CI: 0.97-0.99), GGT (OR: 1.006, 95% CI: 1.001-1.012), age (OR: 5.67, 95% CI: 2.24-14.38), male gender (OR: 2.38, 95% CI: 0.98-5.75), and presence of any comorbidity (OR: 5.23, 95% CI: 2.08-13.13) were associated with mortality. Conclusions: Several clinical and laboratory parameters, such as advanced age, male gender, presence of any comorbidity, and NLR, GGT, CRP and creatinine levels at the time of admission can predict mortality in COVID-19 patients. These parameters obtained at the time of admission can contribute to the reduction of mortality through a closer clinical and laboratory follow-up in these patients. (English) [ FROM AUTHOR] Ama?: Koronavirs hastal 2019 (COVID-19) tan?s? ile takip edilen hastalarda mortalite riskinin erken tespiti ?nemlidir. COVID-19da farkl? klinik ve laboratuvar parametrelerin hastal?k ?iddeti ve mortalite g?stergesi olarak de?erinin saptanmas? hedeflenmi?tir. Gere? ve Y?ntem: COVID-19 tan?s? ile hastaneye yat?r?lan hastalar retrospektif olarak de?erlendirilmi?tir. Hastalar?n yat?? tarihi, taburculuk tarihi, yo?un bak?ma sevk ve ?lm tarihleri, ba?vuru s?ras?ndaki semptomlar?, ba?vuru an?ndaki klinik ve laboratuvar parametreleri kaydedilmi?tir. Bulgular: ?al??maya 168i (%48,4) kad?n olmak zere toplam 347 hasta dahil edildi. Hastalar?n ya? ortalamas? 59,6916,87 (14-97) iken, %40,9u (n=142) 65 ya??n zerindeydi. Hastalar?n %10,1i (n=35) yo?un bak?m nitesine transfer edildi ve %8.4 (n=29) ?ld. Ba?vuru an?ndaki klinik paremetreler de?erlendirildi?inde, oksijen saturasyonu ?len grupta (79,516,95) sa? kalanlara g?re daha d?kt (88,786,11) (p<0,001). Erkek cinsiyet (p=0,05), ileri ya? (p<0,001), pozitif PCR sonucu (p=0,036), ?iddetli toraks BT tutulumu (p<0,001) ve en az bir komorbidite varl (p=0,003) mortalite grubunda daha fazlayd?. ?ok de?i?kenli analizlerde artm?? n?trofil/lenfosit oran? (HR: 1,04, %95 GA: 1,00-1,08), kreatinin (OR: 1,37, %95 CI: 1,13-1,66), CRP (=-0,18, OR: 0,98, 95) % GA: 0,97-0,99), GGT (OR: 1,006, %95 GA: 1,001-1,012), ya? (OR: 5,67, %95 GA: 2,24-14,38), erkek cinsiyet (OR: 2,38, %95 GA: 0,98 -5,75) ve komorbidite varl (OR: 5,23, %95 GA: 2,08-13,13) mortalite ile ili?kili bulundu. Sonu?: COVID-19da ileri ya?, erkek cinsiyet, komorbidite varl ve ba?vuru an?ndaki artm?? NLR, GGT, CRP ve kreatinin de?erleri gibi ?e?itli klinik ve laboratuvar parametreler mortaliteyi ?ng?rmede yard?mc? olabilir. Ba?vuru an?nda elde edilen bu parametrelerle belirlenen hastalar?n daha yak?n klinik ve laboratuvar takibi mortalitenin azalt?lmas?na katk? sa?layacakt?r. (Turkish) [ FROM AUTHOR] Copyright of Istanbul Tip Fakltesi Dergisi is the property of Istanbul Tip Fakultesi Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Nanoscale engineered materials such as nanocomposites can display or be designed to enhance their material properties through control of the internal interfaces. Here, we unveil the nanoscale origin and important characteristics of the enhanced dielectric breakdown capabilities of gold nanoparticle/polymer nanocomposites. Our multiscale approach spans from the study of a single chemically designed organic/inorganic interface to micrometer-thick films. At the nanoscale, we relate the improved breakdown strength to the interfacial charge retention capability by combining scanning probe measurements and density functional theory calculations. At the meso- and macroscales, our findings highlight the relevance of the nanoparticle concentration and distribution in determining and enhancing the dielectric properties, as well as identifying this as a crucial limiting factor for the achievable sample size.

With the advent of the internet among people in recent times, usage of social media and expressing views online has become part of everyone's routine. People are sharing their opinions on social media through text, videos, images, etc. Due to the nature of data shared on social media, it could be used to effectively analyze the emotions of humans, understand and model various events. One such event that happened in recent times is a pandemic due to the Covid-19 virus. Through this paper, we try to compare the emotions and sentiments of people worldwide during four phases of complete and relaxed lockdown through tweets. The four phases of lockdown are defined as Constricted Phase, Semi Constricted Phase, Semi Relaxed Phase, Relaxed Phase. This work will enable the community to provide useful insights and show how people adjusted and how they fought themselves to the pandemic. ? 2021 IEEE.

Although sequencing of the 3 end of the genome of Australian infectious bronchitis viruses (IBVs) has shown that their structural genes are distinct from those of IBVs found in other countries, their replicase genes have not been analysed. To examine this, the complete genomic sequences of the two subpopulations of the VicS vaccine, VicS-v and VicS-del, were determined. Compared with VicS-v, the more attenuated VicS-del strain had two non-synonymous changes in the non-structural protein 6 (nsp6), a transmembrane (TM) domain that may participate in autocatalytic release of the 3-chymotrypsin-like protease, a polymorphic difference at the end of the S2 gene, which coincided with the body transcription-regulating sequence (B-TRS) of mRNA 3 and a truncated open reading frame for a peptide encoded by gene 4 (4b). These genetic differences could be responsible for the differences between these variants in pathogenicity in vivo, and replication in vitro. Phylogenetic analysis of the whole genome showed that VicS-v and VicS-del did not cluster with strains from other countries, supporting the hypothesis that Australian IBV strains have been evolving independently for some time, and analyses of individual polymerase peptide and S glycoprotein genes suggested a distant common ancestor with no recent recombination. This study suggests the potential role of the TM domain in nsp6, the integrity of the S2 protein and the B-TRS 3, and the putative accessory protein 4b, as well as the 3 untranslated region, in the virulence and replication of IBV and has provided a better understanding of relationships between the Australian vaccine strain of IBV and those used elsewhere.

BACKGROUND: The need for protective masks greatly exceeds their global supply during the current COVID-19 pandemic. METHODS: We optimized the temperature used in the dry heat pasteurization method to destroy pathogens and decontaminate masks while retaining their filtering capacity. RESULTS: The current study showed that dry heat at both 60C and 70C for one hour could successfully kill six species of respiratory bacteria and one fungi species, and inactivate the H1N1 indicator virus. After being heated at 70C for 1 h, 2 h, and 3 h, the N95 respirators and surgical face masks showed no changes in their shape and components. The filtering efficiency of bacterial aerosol for N95 respirators were 98%, 98%, and 97% after being heated for 1 h, 2 h, and 3 h, respectively, all of which were over the 95% efficiency required and similar to the value before being heated (99%). The filtering efficiency for surgical face masks was 97%, 97%, and 96% for 1 h, 2 h, and 3 h of heating, respectively, all of which were also similar to the value before being heated (97%). CONCLUSIONS: This method can be used at home and can resolve the current shortage of masks.

This article presents, on the one hand, new algorithms for the fast and stable computation of discrete orthogonal Hahn polynomials of high order (HPs) based on the elimination of all gamma and factorial functions that cause the numerical fluctuations of HPs, and based on the use of appropriate stability conditions. On the other hand, a new method for the fast and numerically stable computation of Hahn moment invariants (HMIs) is also proposed. This method is mainly based on the use of new recursive relations of HPs and of matrix multiplications when calculating HMIs. To validate the efficiency of the algorithms proposed for the calculation of HPs, several signals and large images (4000 4000) are reconstructed by Hahn moments (HMs) up to the last order with a reconstruction error tending towards zero (MSE ? 10(?10)). The efficiency of the proposed method for calculating HMIs is demonstrated on large medical images (2048 2048) with a very low relative error (RE ? 10(?10)). Finally, comparisons with some recent work in the literature are provided.

The presence of respiratory syncytial virus (RSV) was investigated by immunofluorescent antibody (IFA) technique and by an enzyme immunoassay (EIA) in 169 samples of nasopharyngeal secretions of infants and children with acute respiratory infections. Of 31 samples positive by EIA, 25 were positive by IFA. In 24 samples from a retrospective study, RSV positive by IFA and/or tissue culture isolation (TCI), 22 were also positive by EIA. The EIA was also evaluated with 111 RSV isolates in Hep2 cell cultures representing different RSV subgroups. All were positive by EIA. ? 1993 Wiley\Liss, Inc.

OBJECTIVE: To study evaluation of the effectiveness of a comprehensive personalized protocol for the prevention of repeated falls in elderly and senile patients. MATERIAL AND METHODS: Over the course of one year, 300 patients aged 60 and older who suffered two or more falls during the year were observed. Patients of group 1 (n=100) were recommended a comprehensive personalized protocol for the prevention of repeated falls, the observance of which was regularly monitored; patients of group 2 (n=100) received standard recommendations for the prevention of falls upon discharge from the hospital, the observance of which was not actively monitored; patients of group 3 (n=100) were observed by a therapist on an outpatient basis. Primary endpoints: frequency of falls, death from any cause; secondary endpoints: the frequency of fractures, the frequency of hospitalizations for any reason. RESULTS: In group 1, after a year, the frequency of falls decreased by 5 times (100% vs. 21%, p<0.0001), in groups 2 and 3 - by 38% (p=0.013) and 81% (p<0.001). There was no significant decrease in the number of all fractures in any group, but in group 3, the frequency of vertebral fractures increased during the year (p=0.029). Statistically significant positive dynamics of indicators characterizing the geriatric status has been established: walking speed, values on the basic activity scale, a short nutrition assessment scale, the results of the drawing hours test have increased, the intensity of pain has decreased. No one died in group 1, unlike 5 patients in group 2 and 8 in group 3 (p=0.011). CONCLUSION: The use of a comprehensive personalized protocol for the prevention of repeated falls can reduce the number of complications in elderly and senile patients.

BACKGROUND Colon cancer rarely presents with a gastrocolic fistula and resection, if feasible, is usually carried out by open surgery. The authors present the first literature case report of laparoscopic multivisceral resection for gastrocolic fistula secondary to locally advanced colon cancer. MATERIALS AND METHODS A 54-year-old man presented with feculant vomiting, cachexia, and severe iron deficiency anemia. Investigations confirmed a large nonmetastatic splenic flexure colon cancer with fistulation into the stomach. After 10 weeks of nutritional support and laparoscopic defunctioning proximal transverse loop colostomy, we proceeded to laparoscopic extended left hemicolectomy with en bloc sleeve gastrectomy and partial splenectomy. RESULT The procedure was completed laparoscopically (operating time, 400 min; blood loss, 150 mL). He was discharged on the 6th postoperative day after an uneventful recovery. Histology showed an R0 resection of a pT4N1a (1/45 lymph nodes involved) colon cancer with gastrocolic fistula. CONCLUSION Laparoscopic multivisceral en bloc R0 resection of locally advanced colon cancer with gastrocolic fistula can be accomplished safely in experienced hands.

Researchers and practitioners recognize four domains of behavior analysis: radical behaviorism, the experimental analysis of behavior, applied behavior analysis, and the practice of behavior analysis. Given the omnipresence of technology in every sphere of our lives, the purpose of this conceptual article is to describe and argue in favor of a fifth domain: machine behavior analysis. Machine behavior analysis is a science that examines how machines interact with and produce relevant changes in their external environment by relying on replicability, behavioral terminology, and the philosophical assumptions of behavior analysis (e.g., selectionism, determinism, parsimony) to study artificial behavior. Arguments in favor of a science of machine behavior include the omnipresence and impact of machines on human behavior, the inability of engineering alone to explain and control machine behavior, and the need to organize a verbal community of scientists around this common issue. Regardless of whether behavior analysts agree or disagree with this proposal, I argue that the field needs a debate on the topic. As such, the current article aims to encourage and contribute to this debate.

This editorial highlights some of the public health hazards implicit within the government's treatment of migrants and locates these within a wider frame of mental health. In the midst of a pandemic threatening countless lives and a belated lockdown inducing widespread mental stress, the Government continues to pursue a Hostile Environment policy. This involves various legislative and administrative measures aimed at making it as difficult as possible for people without full rights to remain in the UK to actually stay in the country.

Background: A considerable quantity of research supports the findings that the COVID-19 pandemic has significantly influenced individuals psychological wellbeing and behaviours. Purpose: This chapter aims to provide an overview of some of the current studies examining psychological responses of various groups across cultures in relation to the COVID-19 pandemic employing the behavioural immune system (BIS) framework and terror management theory (TMT) as a theoretical lens. Methodology: Online databases are used to conduct a literature review of some of the studies carried out during the global pandemic between 2019 and 2021. Results: The pandemic has had an overall detrimental effect on everyone to some extent, with a disproportionate impact on more vulnerable populations. Conclusion and Recommendation: People continue to cope with the death anxiety from the perspective of the TMT and are driven to avoid pathogens from the BIS viewpoint in the face of the COVID-19 pandemic;however, given the disproportionate impact of the pandemic on vulnerable groups, it is recommended that societies prioritize equity-oriented public health measures to ensure the populations future wellbeing. ? 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Aluminum-containing adjuvants have been used for nearly 100 years to enhance immune responses in billions of doses of vaccines. To date, only a few adjuvants have been approved for use in humans, among which aluminum-containing adjuvants are the only ones widely used. However, the medical need for potent and safe adjuvants is currently continuously increasing, especially those triggering cellular immune responses for cytotoxic T lymphocyte activation, which are urgently needed for the development of efficient virus and cancer vaccines. Manganese is an essential micronutrient required for diverse biological activities, but its functions in immunity remain undefined. We previously reported that Mn(2+) is important in the host defense against cytosolic dsDNA by facilitating cGAS-STING activation and that Mn(2+) alone directly activates cGAS independent of dsDNA, leading to an unconventional catalytic synthesis of 23-cGAMP. Herein, we found that Mn(2+) strongly promoted immune responses by facilitating antigen uptake, presentation, and germinal center formation via both cGAS-STING and NLRP3 activation. Accordingly, a colloidal manganese salt (Mn jelly, MnJ) was formulated to act not only as an immune potentiator but also as a delivery system to stimulate humoral and cellular immune responses, inducing antibody production and CD4(+)/CD8(+) T-cell proliferation and activation by either intramuscular or intranasal immunization. When administered intranasally, MnJ also worked as a mucosal adjuvant, inducing high levels of secretory IgA. MnJ showed good adjuvant effects for all tested antigens, including T cell-dependent and T cell-independent antigens, such as bacterial capsular polysaccharides, thus indicating that it is a promising adjuvant candidate.

Con la pandemia se implementaron diversas estrategias para evitar la intubacin y la ventilacin mecnica invasiva. La posicin prona (PP) tiene claros efectos benficos en mejorar oxigenacin por diversos mecanismos al tiempo que genera cambios hemodinmicos que pueden optimizar la funcin del ventrculo derecho. La evidencia de la PP en pacientes con sndrome de dificultad respiratoria aguda (SDRA) en ventilacin mecnica invasiva (VMI) es contundente y obliga a considerarla en las primeras 24 horas de pacientes con PaO2/FiO2<150. La posicin prona en respiracin espontnea (PPRE) puede mejorar la oxigenacin en pacientes con falla respiratoria e implementada mediante un protocolo que incluye una adecuada seleccin de pacientes puede evitar la intubacin de pacientes en falla respiratoria. La presente revisin resume los antecedentes histricos, las bases fisiolgicas de la posicin prono en el paciente despierto, as como la evidencia que evala su aplicacin en el paciente con COVID-19 al tiempo que resume el protocolo y la experiencia de un centro con esta estrategia como propuesta para estudios multicntricos.

INTRODUCTION: Viruses are major aetiological agents of acute respiratory infection in young children. Although many studies have reported detection and analysis of respiratory viruses in sporadic cases, there have been few follow-up studies of individuals. The purpose of this study was to investigate the frequency of respiratory viral infections in a young child and to examine the duration of viral genome detection in clinical specimens. CASE PRESENTATION: A total of 284 nasal swabs were collected during symptomatic (196 specimens) and asymptomatic (88 specimens) periods of respiratory symptoms from a young female child (from 4 months to 31 months of age, who was admitted to a nursery school at 9 months). Multiplex real-time PCR for 19 respiratory viruses or subtypes was performed. One hundred and ninety-eight of the tested specimens were virus positive (69.7 %) (symptomatic periods, 149/196, 76.0 %; asymptomatic periods, 49/88, 55.7 %). Rhinovirus was the most frequently detected (26 times). Long durations of detection were observed for human coronavirus NL63 (30 days), rhinovirus (28 days) and human bocavirus 1 (22 days). CONCLUSION: Young children living in a group context have a high risk of respiratory virus infections, especially rhinovirus. In some instances, viral genomes were detectable for about 1 month by PCR.

Vitamin D supplementation reduced the risk of acute respiratory tract infection in two meta-analyses. Mendelian randomization shows a causal effect of low vitamin D on bacterial pneumonias risk. These studies involved patients before COVID-19 pandemic. Several association studies found higher incidence of SARS-CoV-2 positivity, greater COVID-19 severity and higher risk of mortality in vitamin D deficient subjects compared to vitamin D non-deficient controls. We draw attention to the trend of inverse relative COVID-19 mortality in Europe versus the states of the Southern Hemisphere (Australia, Brazil, South Africa) in dependence on season, which may be associated with intensity of ultraviolet radiation and consequent seasonal fluctuation of serum vitamin D levels. Although we cannot yet confirm causal role of vitamin D in SARS-CoV-2 positivity or COVID-19, we recommend consumption of vitamin D rich food or vitamin D supplementation in the non-sunny season to prevent vitamin D deficiency.