Effects of Chronic Inflammatory Activation of Murine and Human Arterial Endothelial Cells at Normal Lipoprotein and Cholesterol Levels In Vivo and In Vitro.

The activation of endothelial cells is crucial for immune defense mechanisms but also plays a role in the development of atherosclerosis. We have previously shown that inflammatory stimulation of endothelial cells on top of elevated lipoprotein/cholesterol levels accelerates atherogenesis. The aim of the current study was to investigate how chronic endothelial inflammation changes the aortic transcriptome of mice at normal lipoprotein levels and to compare this to the inflammatory response of isolated endothelial cells in vitro. We applied a mouse model expressing constitutive active IκB kinase 2 (caIKK2)-the key activator of the inflammatory NF-κB pathway-specifically in arterial endothelial cells and analyzed transcriptomic changes in whole aortas, followed by pathway and network analyses. We found an upregulation of cell death and mitochondrial beta-oxidation pathways with a predicted increase in endothelial apoptosis and necrosis and a simultaneous reduction in protein synthesis genes. The highest upregulated gene was ACE2, the SARS-CoV-2 receptor, which is also an important regulator of blood pressure. Analysis of isolated human arterial and venous endothelial cells supported these findings and also revealed a reduction in DNA replication, as well as repair mechanisms, in line with the notion that chronic inflammation contributes to endothelial dysfunction.

Sexually transmitted infections, the epidemic that persists after the COVID-19 pandemic: an analysis of the primary care electronic health records covering about 5 million people in Catalonia.

BACKGROUND: The aim of our study is to analyse the trends in the diagnosis of sexually transmitted infections (STIs) during the COVID-19 pandemic. METHODS: We conducted an observational retrospective population-based study using data from primary care electronic health records spanning from January 2016 to December 2022 (involving 5.1 million people older than 14 years). We described the daily number of new STI diagnoses from 2016 to 2022; as well as the monthly accumulation of new STI diagnoses for each year. We compared the monthly averages of new diagnoses in 2019, 2020, 2021 and 2022 using the T-test. Finally, we performed a segmented regression analysis of the daily number of STI diagnoses. RESULTS: We analysed 200,676 new STI diagnoses. The number of diagnoses abruptly decreased coinciding with the lockdown. Overall in 2020, we observed a reduction of 15%, with higher reductions for specific STIs such as gonorrhoea (-21%), chlamydia (-24%), and HIV (-31%) compared to 2019. Following this drastic drop, which was temporarily associated with the lockdown, we observed a rapid rebound. In 2021, the number of STI diagnoses was similar to that of 2019. Notably, we found a considerable increase in 2022, particularly for non-specific STI, which lack laboratory confirmation (67% increase). HIV was the only STI with a reduction of up to -38% in diagnoses at the end of 2022 compared to 2019. CONCLUSIONS: After a significant reduction in 2020, the number of STIs recorded in primary care rapidly rebounded, and the current trend is similar to that of 2019, except for HIV. These findings underscore the dynamic impact of the COVID-19 pandemic on STI diagnoses and highlight the importance of ongoing monitoring and public health interventions in the post-pandemic period.

¿Es YouTube una herramienta fiable para la enseñanza de cura de hernia inguinal asistida por robot? Una revisión crítica de los recursos disponibles / Is YouTube a reliable tool for approaching robotic assisted transabdominal preperitoneal surgery? A critical review of the available resources

Introducción: La cirugía transabdominal preperitoneal asistida por robot (rTAPP) es una técnica relativamente reciente para el tratamiento de hernia inguinal. Para alcanzar resultados óptimos se deben cumplir las 10 reglas de oro descritas. Los cirujanos en formación suelen revisar vídeos para familiarizarse con nuevas técnicas siendo YouTube una de las plataformas más utilizada. El objetivo de este estudio es realizar una evaluación de los 10 vídeos más vistos en YouTube de reparación de hernia inguinal por rTAPP para determinar si se cumplen las 10 reglas de oro. Métodos: Identificar y evaluar los 10 vídeos con mayor número de visualizaciones relacionados con la rTAPP. Tres Cirujanos con experiencia evaluaron el cumplimiento de las 10 reglas de oro utilizando una escala de Likert. Los datos fueron analizados en Excel (Microsoft) y graficados con Tableau (Tableau Inc). La consistencia entre evaluadores se determinó mediante el alfa de Cronbach, considerándose aceptable un valor > 0,7. Resultados: La evaluación general promedio fue de 3,63 con un rango de 2,6 a 4,9. Las puntuaciones relacionadas con el cumplimiento de las reglas 1, 2, 9, 10 fueron satisfactorias; en cambio, las reglas 3, 4, 5, 7 y 8 fueron débiles, en particular la regla número 7. Se observó consistencia interna entre los evaluadores con un alfa de Cronbach de 0,98. Conclusiones: La falta de cumplimiento con las 10 reglas del oro en la mayoría de los vídeos demuestra que el uso de vídeos (YouTube) no es un adecuado recurso para el aprendizaje de cura de hernia inguinal asistida por robot.(AU)

Introduction: The robotic transabdominal preperitoneal approach (rTAPP) is a relatively recent technique for the treatment of inguinal hernia. To achieve optimal results, the 10 golden rules described must be followed. Surgeons in training often review vídeos to familiarize themselves with new techniques, YouTube being one of the most used platforms. The objective of this study is to carry out an evaluation of the 10 most viewed vídeos on YouTube of inguinal hernia repair by transabdominal preperitoneal approach (rTAPP) to determine if the 10 golden rules are met. Methods: Identify and evaluate the 10 vídeos with the highest number of views related to rTAPP. Three experienced surgeons evaluated compliance with the 10 golden rules using a Likert scale. Data were analyzed in Excel (Microsoft) and plotted with Tableau (Tableau Inc.). The consistency between evaluators was determined using Cronbach's alpha, considering a value >0.7 acceptable. Results: The average overall evaluation was 3.63 with a range of 2.6–4.9. The scores related to compliance with the rules 1, 2, 9 and 10 were satisfactory; on the other hand, rules 3, 4, 5, 7 and 8 were weak, particularly rule number 7. Internal consistency was observed between raters with a Cronbach's alpha of 0.98.Conclusions: The lack of compliance with the 10 golden rules in most of the vídeos demonstrates that the use of vídeos (YouTube) is not an adequate resource for learning robot-assisted inguinal hernia cure.(AU)

Antibody Seroprevalence to Spotted Fever Group Rickettsiae in Miraflores, Colombia: A Cross-Sectional Study in Humans and Dogs.

Tick-borne disease burdens are increasing globally, impacting mostly rural and vulnerable communities. Among the most important emerging tick-borne pathogens are the Rickettsia species within the spotted fever group (SFGR) because of their genetic diversity and high lethality rate. Colombia is highly affected by SFGR despite not being reportable diseases; thus, research and clinical management are neglected. Although some departments have demonstrated high seroprevalence rates, in others, such as Boyacá Department, seroprevalence is unknown. Rickettsioses have not been described in Boyacá since 1943, and conversations with local physicians raised suspicions of recent undiagnosed disease compatible with rickettsiosis in some rural areas of the department, warranting epidemiological investigation. Using biobanked human and canine samples from a previous 2021 vector-borne disease study in Miraflores municipality, Boyacá, we had an opportunity to unearth SFGR's exposure in the region. Samples were evaluated using IgG indirect fluorescent assays against SFGR and complemented by survey questionnaires evaluating associated factors. Findings yielded first-time SFGR serological evidence in Boyacá with a 26.5% seroprevalence among dogs and a 20.4% among humans. Human and dog seroprevalences were positively associated, suggesting the presence of domestic transmission. Owning a greater number of domestic animals (prevalence ratio adjusted for all measured factors [aPR], 1.52) and living near crop fields (aPR, 7.77) were associated with an increased likelihood of household seropositivity. Our findings are consistent with the literature in Colombia, uncovering a suspected region where the disease is endemic. Future studies are warranted to continue defining high-risk areas to determine public health intervention plans.

Anti-PD-1 chimeric antigen receptor T cells efficiently target SIV-infected CD4+ T cells in germinal centers.

Programmed cell death protein 1 (PD-1) is an immune checkpoint marker commonly expressed on memory T cells and enriched in latently HIV-infected CD4+ T cells. We engineered an anti-PD-1 chimeric antigen receptor (CAR) to assess the impact of PD-1 depletion on viral reservoirs and rebound dynamics in SIVmac239-infected rhesus macaques (RMs). Adoptive transfer of anti-PD-1 CAR T cells was done in 2 SIV-naive and 4 SIV-infected RMs on antiretroviral therapy (ART). In 3 of 6 RMs, anti-PD-1 CAR T cells expanded and persisted for up to 100 days concomitant with the depletion of PD-1+ memory T cells in blood and tissues, including lymph node CD4+ follicular helper T (TFH) cells. Loss of TFH cells was associated with depletion of detectable SIV RNA from the germinal center (GC). However, following CAR T infusion and ART interruption, there was a marked increase in SIV replication in extrafollicular portions of lymph nodes, a 2-log higher plasma viremia relative to controls, and accelerated disease progression associated with the depletion of CD8+ memory T cells. These data indicate anti-PD-1 CAR T cells depleted PD-1+ T cells, including GC TFH cells, and eradicated SIV from this immunological sanctuary.

Is YouTube a reliable tool for approaching robotic assisted transabdominal preperitoneal surgery? A critical review of the available resources.

INTRODUCTION: The robotic transabdominal preperitoneal approach (rTAPP) is a relatively recent technique for the treatment of inguinal hernia. To achieve optimal results, the 10 golden rules described must be followed. Surgeons in training often review videos to familiarize themselves with new techniques, YouTube being one of the most used platforms. The objective of this study is to carry out an evaluation of the 10 most viewed videos on YouTube of inguinal hernia repair by transabdominal preperitoneal approach (rTAPP) to determine if the 10 golden rules are met. METHODS: Identify and evaluate the 10 videos with the highest number of views related to rTAPP. Three experienced Surgeons evaluated compliance with the 10 golden rules using a Likert scale. Data were analyzed in Excel (Microsoft) and plotted with Tableau (Tableau Inc). The consistency between evaluators was determined using Cronbach's alpha, considering a value >0.7 acceptable. RESULTS: The average overall evaluation was 3.63 with a range of 2.6 to 4.9. The scores related to compliance with the rules 1, 2, 9, 10 were satisfactory; on the other hand, rules 3, 4, 5, 7 and 8 were weak, particularly rule number 7. Internal consistency was observed between raters with a Cronbach's alpha of 0.98. CONCLUSIONS: The lack of compliance with the 10 golden rules in most of the videos demonstrates that the use of videos (YouTube) is not an adequate resource for learning robot-assisted inguinal hernia cure.

Influence of dengue virus serotypes on the abundance of Aedes aegypti insect-specific viruses (ISVs).

A comprehensive understanding of the virome in mosquito vectors is crucial for assessing the potential transmission of viral agents, designing effective vector control strategies, and advancing our knowledge of insect-specific viruses (ISVs). In this study, we utilized Oxford Nanopore Technologies metagenomics to characterize the virome of Aedes aegypti mosquitoes collected in various regions of Colombia, a country hyperendemic for dengue virus (DENV). Analyses were conducted on groups of insects with previous natural DENV infection (DENV-1 and DENV-2 serotypes), as well as mosquito samples that tested negative for virus infection (DENV-negative). Our findings indicate that the Ae. aegypti virome exhibits a similar viral composition at the ISV family and species levels in both DENV-positive and DENV-negative samples across all study sites. However, differences were observed in the relative abundance of viral families such as Phenuiviridae, Partitiviridae, Flaviviridae, Rhabdoviridae, Picornaviridae, Bromoviridae, and Virgaviridae, depending on the serotype of DENV-1 and DENV-2. In addition, ISVs are frequently found in the core virome of Ae. aegypti, such as Phasi Charoen-like phasivirus (PCLV), which was the most prevalent and showed variable abundance in relation to the presence of specific DENV serotypes. Phylogenetic analyses of the L, M, and S segments of the PCLV genome are associated with sequences from different regions of the world but show close clustering with sequences from Brazil and Guadeloupe, indicating a shared evolutionary relationship. The profiling of the Ae. aegypti virome in Colombia presented here improves our understanding of viral diversity within mosquito vectors and provides information that opens the way to possible connections between ISVs and arboviruses. Future studies aimed at deepening our understanding of the mechanisms underlying the interactions between ISVs and DENV serotypes in Ae. aegypti could provide valuable information for the design of effective vector-borne viral disease control and prevention strategies.IMPORTANCEIn this study, we employed a metagenomic approach to characterize the virome of Aedes aegypti mosquitoes, with and without natural DENV infection, in several regions of Colombia. Our findings indicate that the mosquito virome is predominantly composed of insect-specific viruses (ISVs) and that infection with different DENV serotypes (DENV-1 and DENV-2) could lead to alterations in the relative abundance of viral families and species constituting the core virome in Aedes spp. The study also sheds light on the identification of the genome and evolutionary relationships of the Phasi Charoen-like phasivirus in Ae. aegypti in Colombia, a widespread ISV in areas with high DENV incidence.

An Outbreak of Acute Chagas Disease Possibly Spread through Oral Transmission Involving Animal Reservoirs in Eastern Colombia.

Chagas disease (CD) is a parasitic infection caused by the parasite Trypanosoma cruzi. Reports of CD cases associated with oral transmission have increased, particularly in Colombia, Brazil, and Venezuela. In this investigation, parasitological, serological, and molecular tests were conducted on samples obtained from humans, mammal reservoirs, and hosts involved in the assessment of a suspected oral transmission outbreak in Cubara, Boyaca, Colombia. Seropositivity was observed in 60% (3 of 5) of index patients and 6.4% (5 of 78) of close contacts. Trypanosoma cruzi DNA was detected by quantitative polymerase chain reaction in 100% of index cases, 6.4% (5 of 78) of close contacts, 60% (6 of 10) of canines, and 100% (5 of 5) of opossums. In all index cases, the TcI lineage was identified, along with two cases of mixed infection (TcI/TcII-TcVI). Hemoculture revealed a flagellate presence in 80% of opossums, whereas all triatomine bugs tested negative. Our findings suggest a potential oral transmission route through contamination with opossum secretions.

Seed amplification assay results illustrate discrepancy in Parkinson's disease clinical diagnostic accuracy and error rates.

Parkinson's disease (PD) may be misdiagnosed due to the clinical overlap between PD and atypical parkinsonism. The utility of α-Synuclein (αSyn) Seed Amplification Assay (SAA) as a diagnostic indicator for PD has been reported in numerous studies, but never when administered as a validated clinical laboratory test. This study compares results from αSyn-SAA validation testing performed using well-characterized cohorts from two biorepositories to better understand the accuracy of PD clinical diagnosis. Blinded cerebrospinal fluid (CSF) specimens from a repository that included cohorts of subjects clinically diagnosed as PD or healthy controls, both with confirmatory dopamine transporter single-photon emission computed tomography (DAT SPECT) imaging, and blinded CSF specimens from a repository that included cohorts of subjects clinically diagnosed as PD or healthy controls based on clinical diagnosis alone, were tested as part of the validation studies for the diagnostic αSyn-SAA test (SYNTap® Biomarker Test). Measured αSyn-SAA test accuracy was 83.9% using clinical diagnosis as comparator, and 93.6% using clinical diagnosis with confirmatory DAT- SPECT imaging as comparator. The statistically significant discordance between accuracy determinations using specimens classified using different diagnostic inclusion criteria indicates that there is some symbiosis between dopamine-weighted imaging and αSyn-SAA results, both of which are associated with higher accuracy compared with the clinical diagnosis alone.

Mortality in Catalonia during the summer of 2022 and its relation with high temperatures and COVID-19 cases.

Purpose: To analyse the association between the mortality during the summer 2022 and either high temperatures or the COVID-19 wave with data from the Catalan Health Care System (7.8 million people). Methods: We performed a retrospective study using publicly available data of meteorological variables, influenza-like illness (ILI) cases (including COVID-19) and deaths. The study comprises the summer months of the years 2021 and 2022. To compare the curves of mortality, ILI and temperature we calculated the z-score of each series. We assessed the observed lag between curves using the cross-correlation function. Finally, we calculated the correlation between the z-scores using the Pearson correlation coefficient (R2). Results: During the study period, 33,967 deaths were reported in Catalonia (16,416 in the summer of 2021 and 17,551 in the summer of 2022). In 2022, the observed lag and the correlation between the z-scores of temperature and all-cause deaths was 3 days and R2 = 0.86, while between ILI and all-cause deaths was 22 days and R2 = 0.21. This high correlation between temperature and deaths increased up to 0.91 when we excluded those deaths reported as COVID-19 deaths, while the correlation between ILI and non-COVID-19 deaths decreased to -0.19. No correlation was observed between non-COVID deaths and temperature or ILI cases in 2021. Conclusion: Our study suggests that the main cause of the increase in deaths during summer 2022 in Catalonia was the high temperatures and its duration. The contribution of the COVID-19 seems to be limited.

Accidental implant screwdriver aspiration: A case series report with literature review and proposed action protocol.

This article presents the first reported case series of three cases of aspiration of a dental implant screwdriver, which was successfully removed by flexible bronchoscopy. The report highlights preventive measures that can be taken in the dental office and the clinical signs and symptoms of the presence of a dental implant screwdriver in the bronchial tree. The nine reports published to date on this phenomenon are reviewed and compared, and an action protocol for dental practitioners, anaesthetists and pulmonologists is proposed to address this emergency. Some early and late complications are also described.

Polarisation compensation in non-planar image-rotating OPO ring resonators.

Non-planar image-rotating OPO ring resonators necessitate polarisation compensation in contrast to their planar counterparts. This is essential for maintaining phase matching conditions for non-linear optical conversion in the resonator during each cavity round trip. In this study, we examine the polarisation compensation and its impact on the performance of two types of non-planar resonators: RISTRA with a π2 image rotation and FIRE with a fractional image rotation (π2 fraction). The RISTRA is insensitive to mirror phase shifts, while the FIRE has a more complex dependence of polarisation rotation on mirror phase shifts. There has been debate over whether a single birefringent element can provide adequate polarisation compensation for non-planar resonators beyond RISTRA-type. Our results show that under certain experimentally feasible conditions, even FIRE resonators can achieve adequate polarisation compensation with a single half-wave plate. We validate our theoretical analysis through numerical simulations and experimental studies of OPO output beam polarisation using ZnGeP2 non-linear crystals.

Impact on Glycemic Variation Caused by a Change in the Dietary Intake Sequence.

This work presents an analysis of the effect on glycemic variation caused by modifying the macronutrient intake sequence in a person without a diagnosis of diabetes. In this work, three types of nutritional studies were developed: (1) glucose variation under conditions of daily intake (food mixture); (2) glucose variation under conditions of daily intake modifying the macronutrient intake sequence; (3) glucose variation after a modification in the diet and macronutrient intake sequence. The focus of this research is to obtain preliminary results on the effectiveness of a nutritional intervention based on the modification of the sequence of macronutrient intake in a healthy person during 14-day periods. The results obtained corroborate the positive effect on the glucose of consuming vegetables, fiber, or proteins before carbohydrates, decreasing the peaks in the postprandial glucose curves (vegetables: 113-117 mg/dL; proteins: 107-112 mg/dL; carbohydrates: 115-125 mg/dL) and reducing the average levels of blood glucose concentrations (vegetables: 87-95 mg/dL; proteins: 82-99 mg/dL; carbohydrates: 90-98 mg/dL). The present work demonstrates the preliminary potential of the sequence in the macronutrient intake for the generation of alternatives of prevention and solution of chronic degenerative diseases, improving the management of glucose in the organism and permeating in the reduction of weight and the state of health of the individuals.

Perforación traqueal diferida tras cirugía tiroidea en un paciente con radioterapia cervical.

Tracheal perforation is a rare complication of thyroid surgery. A 36-year-old man with previous neck radiotherapy due to a nasopharyngeal cancer. After right hemithyoidectomy and isthmusectomy, the patient presented a tracheal perforation. The diagnosis was confirmed with computed tomography and bronchoscopy. A conservative management was performed with drainage and antibiotic therapy, and the evolution was satisfactory. If recognized at the time of the surgery, perforations should be closed primarily. Delayed perforations will be treated with an emergency surgery or conservatively depending on the clinical situation of the patient.

La perforación traqueal es una rara complicación de la cirugía tiroidea. Varón de 36 años con antecedente de radioterapia cervical por una neoplasia de cavum sometido a hemitiroidectomía derecha e istmectomía que durante el posoperatorio presentó una perforación traqueal confirmada por tomografía computarizada y broncoscopia. Se realizó manejo conservador con drenaje y antibioticoterapia, evolucionando de forma favorable. Las perforaciones identificadas durante la cirugía deben ser reparadas intraoperatoriamente, mientras que las diferidas se tratarán de forma quirúrgica urgente o de manera conservadora en función de la situación clínica del paciente.

"Decline and uneven recovery from 7 common long-term conditions managed in the Catalan primary care after two pandemic years: an observational retrospective population-based study using primary care electronic health records".

BACKGROUND: The incidence of chronic diseases during the COVID-19 pandemic has drastically been reduced worldwide due to disruptions in healthcare systems. The aim of our study is to analyse the trends in the incidence of 7 commonly managed primary care chronic diseases during the last 2 years of the COVID-19 pandemic in Catalonia. METHODS: We performed an observational retrospective population-based study using data from primary care electronic health records from January 2018 to August 2022 (5.1 million people older than 14 years). We divided the study period into two: a pre-pandemic period (before 14 March 2020) and a pandemic period. We performed a segmented regression analysis of daily incidence rates per 100,000 inhabitants of 7 chronic diseases: type 2 diabetes mellitus (T2DM), asthma, chronic obstructive pulmonary disease (COPD), ischemic heart disease (IHD), heart failure (HF), hypertension and hypercholesterolemia. In addition, we compared annual incidence between pandemic years (2020, 2021 and 2022) and 2019. Associated incidence rate ratios (IRR) were also calculated. Finally, we estimated the number of expected diagnoses during the pandemic period using data from 2019 and we compared it with the observed data. RESULTS: We analysed 740,820 new chronic diseases' diagnoses. Daily incidence rates of all 7 chronic diseases were drastically interrupted on 14 March 2020, and a general upward trend was observed during the following months. Reductions in 2020 were around 30% for all conditions except COPD which had greater reductions (IRR: 0.58 [95% CI: 0.57 to 0.6]) and HF with lesser drops (IRR: 0.86 [95% CI: 0.84 to 0.88]). Some of the chronic conditions have returned to pre-pandemic diagnosis levels, except asthma, COPD and IHD. The return to pre-pandemic diagnosis levels compensated for the drops in 2020 for T2DM and HF, but not for hypertension which presented an incomplete recovery. We also observed an excess of hypercholesterolemia diagnoses of 8.5% (95%CI: 1.81% to 16.15%). CONCLUSIONS: Although primary care has recovered the pre-pandemic diagnosis levels for some chronic diseases, there are still missing diagnoses of asthma, COPD and IHD that should be addressed.

Cancer diagnosis in primary care after second pandemic year in Catalonia: a time-series analysis of primary care electronic health records covering about 5 million people.

BACKGROUND: During the COVID-19 pandemic, the incidence of chronic disease had drastically been reduced due to health care interruptions. The aim of this study is to analyse cancer diagnosis during the last 2 years of the COVID-19 pandemic. METHODS: Time-series study of cancer diagnoses recorded in primary care settings, using data from the primary care electronic health records from January 2014 to December 2021. We obtained the expected monthly rate per 100,000 inhabitants using a time regression adjusted by trend and seasonality. We additionally compared rates of cancer diagnoses in 2019 with those of 2020 and 2021 using the t-test. We performed the analysis globally, by sex and by type of cancer. RESULTS: In 2020, the rate of cancer diagnoses had reduced by -21% compared to 2019 (P < 0.05). Greater reductions were observed during the lockdown in early 2020 (>40%) and with some types of cancers, especially prostate and skin cancers (-29.6% and -26.9%, respectively, P < 0.05). Lung cancers presented statistically non-significant reductions in both years. Cancer diagnosis returned to expected around March 2021, and the rate in 2021 was similar to that of 2019 (overall difference of 0.21%, P = 0.967). However, an 11% reduction was still found when comparing the pandemic months of 2020-2021 with pre-pandemic months. CONCLUSIONS: Although primary care cancer diagnoses in 2021 have returned to pre-pandemic levels, missing diagnoses during the last 2 years have not been fully recovered.

Unravelling the role of the mandatory use of face covering masks for the control of SARS-CoV-2 in schools: a quasi-experimental study nested in a population-based cohort in Catalonia (Spain).

OBJECTIVE: To assess the effectiveness of mandatory use of face covering masks (FCMs) in schools during the first term of the 2021-2022 academic year. DESIGN: A retrospective population-based study. SETTING: Schools in Catalonia (Spain). POPULATION: 599 314 children aged 3-11 years attending preschool (3-5 years, without FCM mandate) and primary education (6-11 years, with FCM mandate). STUDY PERIOD: From 13 September to 22 December 2021 (before Omicron variant). INTERVENTIONS: A quasi-experimental comparison between children in the last grade of preschool (5 years old), as a control group, and children in year 1 of primary education (6 years old), as an interventional group. MAIN OUTCOME MEASURES: Incidence of SARS-CoV-2, secondary attack rates (SARs) and effective reproductive number (R*). RESULTS: SARS-CoV-2 incidence was significantly lower in preschool than in primary education, and an increasing trend with age was observed. Six-year-old children showed higher incidence than 5 year olds (3.54% vs 3.1%; OR 1.15 (95% CI 1.08 to 1.22)) and slightly lower but not statistically significant SAR (4.36% vs 4.59%; incidence risk ratio 0.96 (95% CI 0.82 to 1.11)) and R* (0.9 vs 0.93; OR 0.96 (95% CI 0.87 to 1.09)). Results remained consistent using a regression discontinuity design and linear regression extrapolation approaches. CONCLUSIONS: We found no significant differences in SARS-CoV-2 transmission due to FCM mandates in Catalonian schools. Instead, age was the most important factor in explaining the transmission risk for children attending school.