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School closures were enforced as measures to restrain the COVID-19 pandemic, based on the assumption that young children may play a key role in SARS-CoV-2 spread. This study aims to determine the prevalence of SARS-CoV-2 IgG antibodies in children and corresponding parents, in order to improve surveillance and estimate the prevalence of asymptomatic or subclinical COVID-19 cases. A prospective multicenter study was conducted between March and June 2021 in Greece. Children admitted to the hospital or examined in outpatient clinics for reasons other than COVID-19 and their parents were tested for anti-Spike SARS-CoV-2 IgG in serum. A questionnaire about clinical and demographic data was completed. The study included 823 participants: 427 children and 396 corresponding parents. The overall seroprevalence was 16.4% in parents and 13.8% in children. Among families with ≥ 1 seropositive child or parent, the combination of a seropositive parent and a corresponding seronegative child was 29.6%, a seronegative parent and a corresponding seropositive child was 24.7%, and a seropositive child with a corresponding seropositive parent was 45.7%. Age, level of education, and school or work attendance were not significantly associated with increased seropositivity. On the contrary, ethnic minority of Roma, close contact with known COVID-19 case, previous symptoms consistent with COVID-19, and mass gatherings were risk factors for seropositivity.The spread of SARS-CoV-2 during a period of lockdown in Greece was low in children and comparable to adults most likely due to intrafamilial transmission. Accordingly, it is unlikely that children have boosted virus transmission.• In the earliest months of the pandemic, it was demonstrated that children had significantly lower seroprevalence rates than the older age groups, due to the fact that children had decreased exposure to the virus, because of early public health interventions, such as school and day care closure. • Later, further studies reported that children have similar incidence rate of SARS-CoV-2 infection compared to adults in households and community settings.• In this seroprevalence study, the spread of SARS-CoV-2 infection during a period of lockdown in Greece with the predominance of the Alpha-variant was particularly low in children and comparable to adults, most likely due to intrafamilial transmission. • These study findings will be useful for decisions regarding non-pharmaceutical interventions during the pandemic, and especially, to guide in designing and implementing appropriate containment measures for schools and social gatherings.

Rotavirus group A (RVA) is characterized by molecular and epidemiological diversity. To date, 42 G and 58 P RVA genotypes have been identified, some of which, like P[14], have a zoonotic origin. In this study, we describe the epidemiology of unusual RVA genotypes and the molecular characteristics of P[14] strains. Fecal samples from children ≤ 16 years of age with acute gastroenteritis (AGE) who were hospitalized during 2007–2021 in Greece were tested for RVA by immunochromatography. Positive RVA samples were G and P genotyped, and part of the VP7 and VP4 genes were sequenced by the Sanger method. Epidemiological data were also recorded. Phylogenetic analysis of P[14] was performed using MEGA 11 software. Sixty-two (1.4%) out of 4427 children with RVA AGE were infected with an unusual G (G6/G8/G10) or P (P[6]/P[9]/P[10]/P[11]/P[14]) genotype. Their median (IQR) age was 18.7 (37.3) months, and 67.7% (42/62) were males. None of the children were vaccinated against RVA. P[9] (28/62; 45.2%) was the most common unusual genotype, followed by P[14] (12/62; 19.4%). In the last two years, during the period of the COVID-19 pandemic, an emergence of P[14] was observed (5/12, 41.6%) after an 8-year absence. The highest prevalence of P[14] infection was seen in the spring (91.7%). The combinations G8P[14] (41.7%), G6P[14] (41.7%), and G4P[14] (16.6%) were also detected. Phylogenetic analysis showed a potential evolutionary relationship of three human RVA P[14] strains to a fox strain from Croatia. These findings suggest a possible zoonotic origin of P[14] and interspecies transmission between nondomestic animals and humans, which may lead to new RVA genotypes with unknown severity.

To examine whether immunization time affects the immune responses elicited by the BNT162b2 COVID-19 vaccine, we investigated the possible association between total SARS-CoV-2 spike protein receptor binding domain (TAbs-RBD) and neutralizing (NAbs-RBD) antibodies with vaccination time. A cohort of 468 healthcare workers (mean age [±SD]: 48 [±13] years), were included in the study. One month after the second dose, healthcare workers who were vaccinated between 1500-2200 h had higher TAbs-RBD compared to 0700-1100 h and 1100-1500 h ( p = 0.006). One month after the third dose, healthcare workers who were vaccinated between 0700-1100 h and 1500-2200 h had significantly higher TAbs-RBD compared to 1100-1500 h ( p = 0.034). However, no association of NAbs-RBD with vaccination time was detected after each of the 3 doses ( p > 0.4). Despite the possible effect of BNT162b2 vaccination time in TAbs-RBD levels, possibly due to rhythmic expression of clock genes, neutralizing activity was not associated with vaccination time and, therefore, further investigation is required.

This randomized study investigates whether feeding very low birth weight (VLBW) infants with mother’s own milk (MOM) supplemented with either preterm (PDM) or term donor milk (TDM), when MOM is insufficient, has a positive impact on infants’ protein intake and growth. A hundred and twenty VLBW infants were randomized into two groups. Group A (43 infants) received MOM supplemented with PDM, whereas Group B (77 infants) was fed with MOM supplemented with TDM, for the first three weeks of life (donor milk period). Breast milk fortifier was added when milk feeds exceeded 50 mL/Kg/day. After the donor milk period, both groups were fed with formula when MOM was not available or the milk bank was unable to provide TDM. Protein intake was higher in Group A than in Group B at initiation of milk fortification (p = 0.006), as well as during the 3-week donor milk period (p = 0.023) and throughout hospitalization (p = 0.014). Moreover, Group A presented higher Δz-score for body weight (p = 0.019) and head circumference (p = 0.001) from birth to the end of donor milk period, and higher mean body weight at discharge (p = 0.047) compared to Group B. In conclusion, when donor milk is required, PDM positively impacts protein intake and growth in VLBW infants (NCT05675397).

Cellular immunity after SARS-CoV-2 infection or immunization may be important for long-lasting protection against severe COVID-19 disease. We investigated cellular immune responses after SARS-CoV-2 infection and/or vaccination with an interferon (IFN)-γ release assay (QuantiFERON, QFN). In parallel, we measured SARS-CoV-2 anti-Nucleocapsid (Abs-N), anti-Spike (Abs-S) and Neutralizing (NAbs) antibodies against SARS-CoV-2 wild type and Omicron variant. We recruited 41 participants: unvaccinated children and adults and vaccinated uninfected or vaccinated convalescent adults. All vaccinated adults had received three doses of the BNT162b2 COVID-19 vaccine at 6.2–10.9 months prior to their inclusion to the study. All the unvaccinated participants were tested negative with QFN. Regarding the vaccinated population, 50% (8/16) of the vaccinated uninfected adults and 57.1% (8/14) of the vaccinated convalescent adults were tested positive. Among the QFN positive individuals, a reactive response to antigen (Ag) 1 (CD4+ epitopes) and to Ag2 (CD4+ and CD8+ epitopes), was detected in 68.8% (11/16) and 87.5% (14/16) respectively, while 56.3% (9/16) had a reactive response to both antigens. Additionally, Ag1 IFN-γ values correlated with Abs-S (P P = 0.039) levels, but not with NAbs against Omicron variant (P = 0.09) and Ag2 IFN-γ values correlated only with Abs-S levels (P = 0.009). The SARS-CoV-2 QFN assay did not detect T cellular responses in unvaccinated individuals and in a significant number of vaccinated individuals. Further comparative studies with different immunology assays are required to elucidate whether this is the result of waning immunity or low sensitivity of the assay.

Background Data regarding cell-mediated immunological differences in children across COVID-19 clinical spectrum are limited. We prospectively investigated Spike-protein specific cellular immunity in children with symptomatic COVID-19 or MIS-C, by single cell cytokine expression profiling. Methods PBMCs from children with MIS-C, symptomatic COVID-19 (one month after hospitalization) and healthy controls were isolated prospectively. Cell suspensions were divided into two quantitatively equal samples (a negative control-unstimulated and a positive-stimulated). Cells stimulation was performed using SARS-CoV-2 Spike antigenic peptides mix (Peptivator SARS-CoV-2 Prot_S). Cells of each sample were stained with fluorochrome monoclonal antibodies against 8 surface markers (CD3, CD4, CD8, CD14, CD19, CD137, CD197, CD45RA) and 6 intracellular markers (IL-4, IL-2, IL-17, IFN-γ, TNF-α, Granzyme B). Viability was assessed by 7AAD. Stained cell preparations were analysed using 13 colour Flow Cytometry (DX Flex, Beckman Coulter). Flow cytometric analysis was performed using Kaluza 2.1 Software. Results Sixteen children (4 MIS-C, 8 post-COVID-19 and 4 healthy controls) were included in the study. The mean age (±SD) of the participants was 11.22 years (±3.48). Children with MIS-C had significantly higher mean (±SD) values of CD8+IFN-γ/million CD3+ [226.68 (134.92) vs 45.43 (57.28); P: 0.033] and median (IQR) of CD8+IFN-γ/ml [156.38 (184.13) vs 26.34 (82.36);P: 0.033] compared to symptomatic COVID-19 children. Compared to healthy controls, MIS-C patients had significantly higher median (IQR) values of CD4+IL-2/million CD3+ [923.12 (3777.95) vs 97.59 (71.71); P: 0.042] and CD4+IL-2/ml median (IQR) [626.33 (2744.98) vs 169.3 (173.91); P: 0.042]. No other significant differences were observed regarding other immunological markers in 3 study groups. Conclusion IFN-γ production by CD8+ T cells is highly expressed in children with MIS-C compared to hospitalized children one month after acute COVID-19 and could consist possible immunological biomarker. Further studies are needed in order to elucidate the pathophysiological basis of these findings. Disclosures All Authors: No reported disclosures.

Background Two rotavirus (RV) vaccines were licensed in Greece in late 2006 and included in the national immunisation programme in 2012. Aim To study the epidemiology and genotype distribution of RV in children during the post-vaccination period and assess the impact of increased vaccination coverage. Methods In a prospective multicentre hospital-based study, hospitalised children (≤ 16 years) with an RV-positive faecal sample were recruited. Epidemiological and genotyping analyses were performed; periods of low (2008–12) and moderate (2012–20) RV vaccination coverage were compared. Statistical analysis was performed with a chi-squared or Mann–Whitney U test and logistic regression. Results A total of 3,874 children (55.6% male; n = 2,153) with median age of 1.4 years (IQR: 0.5–3.3) were studied during 2008–20. Most RV-infected children were aged ≤ 3 years (72.2%) and hospitalised during December–May (69.1%). Common RV genotypes (G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], G12P[8]) were detected in 92.2% of samples; G-P combinations with prevalence above 1% were G4P[8] (44.1%), G1P[8] (25.4%), G2P[4] (14.9%), G9P[8] (3.5%), G12P[8] (2.2%), G3P[8] (2.1%), other (4.3%) and mixed (3.5%). Of all samples, 97.6% were homotypic or partially heterotypic to vaccines’ genotypes. With moderate vaccination coverage, the seasonal peak was detected earlier, children were older and partially or fully heterotypic genotypes were increased (p Conclusions In the era of moderate RV vaccination coverage in Greece, epidemiology of RV in hospitalised children seemed to change. However, most circulating genotypes remain homotypic or partially heterotypic to RV vaccines. Continuous epidemiological surveillance and genotyping are important to monitor possible changes arising from RV vaccines’ implementation.

Limited prospective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) data in children regarding the impact of Omicron variant in seropositivity have been reported. We investigated SARS-CoV-2 seropositivity in children between 1 September 2021 and 30 April 2022, representing Delta and Omicron predominance periods. Serum samples from children admitted to the major tertiary Greek paediatric hospital for any cause, except for COVID-19, were randomly collected and tested for SARS-CoV-2 natural infection antibodies against nucleocapsid antigen (Elecsys® Anti-SARS-CoV-2 reagent). A total of 506/1312 (38.6%) seropositive children (0–16 years) were detected (males: 261/506(51.6%); median age (IQR): 95.2 months(24–144)). Seropositivity rates (%) increased from Delta to Omicron period from 29.7% to 48.5% (P-valueP-value:0.914). The highest seropositivity rate was detected in April 2022 (52.6%) and reached 73.9% specifically for the age group 12–16 years. No significant differences were detected in seropositivity with respect to gender, origin, or hospitalisation status. Median (IQR) antibody titres were higher in the Omicron vs. Delta period in all age groups, especially in 12–16 years [32.2 COI (7–77.1) vs. 11.4 COI(2.8–50.2), P-value:0.009). During Omicron variant period increased SARS-CoV-2 seropositivity was detected in paediatric population, especially in adolescents, implicating either increased transmissibility or reinfection rates.

Rotavirus A (RVA) is characterized by molecular and epidemiological diversity. To date, 42G and 58P RVA genotypes have been identified, some of which have zoonotic origin, like P[14]. This study aims at the epidemiological and molecular characterization of human P[14] RVA. Fecal samples from children ≤ 16 years with acute gastroenteritis (AGE), hospitalized during 01/2007-12/2021, were tested for RVA by chromatographic immunoassay. Demographic, clinical and laboratory data were recorded. Positive RVA samples were G and P typed performing Sanger sequencing. Phylogenetic analysis of P[14] was performed using the Mega X software. Sixty (1.36%) out of 4427 children with RVA AGE, were infected with an unusual G (G6/G8/G10) or P (P[6]/P[9]/P[10]/P[11]/P[14]) genotype. P[9] (27/60; 45%) was the most common unusual genotype followed by P[14] (11/60; 18.3%). Median age of children with P[14] was 37.8 months (IQR:17.6–77.1), 6/11 were males and 4/11 resided to rural areas. Their symptoms were diarrhea (9/11; 81.8%), vomiting (7/11; 63.6%), fever (7/11; 63.6%) and moderate dehydration (6/11; 54.5%). All children were unvaccinated for RVA. Seasonal peak of P[14] was during spring (91%). The combinations G8P[14] (45.5%), G6P[14] (36.4%) and G4P[14] (18.1%) were detected. Phylogenetic analysis showed potential evolutionary relationship of three human RVA P[14] with a fox strain from Croatia. These findings enhance the potential zoonotic origin of P[14] and the interspecies transmission between nondomestic animals and humans, which may lead to new RVA genotypes with unknown severity.

Host immune responses to severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), especially in children, are still under investigation. Children with coronavirus disease 2019 (COVID‐19) constitute a significant study group of immune responses as they rarely present with severe clinical manifestations, require hospitalization, or develop complications such as multisystem inflammatory syndrome in children (MIS‐C) associated with SARS‐CoV‐2 infection. The deciphering of children’s immune responses during COVID‐19 infection will provide information about the protective mechanisms, while new potential targets for future therapies are likely to be revealed. Despite the limited immunological studies in children with COVID‐19, this review compares data between adults and children in terms of innate and adaptive immunity to SARS‐CoV‐2, discusses the possible reasons why children are mostly asymptomatic, and highlights unanswered or unclear immunological issues. Current evidence suggests that the activity of innate immunity seems to be crucial to the early phases of SARS‐CoV‐2 infection and adaptive memory immunity is vital to prevent reinfection., Despite the limited immunological studies from children with COVID‐19, this review compares data between adults and children in terms of innate and adaptive immunity to SARS‐CoV‐2, discusses the possible reasons why children are mostly asymptomatic, and highlights unanswered or unclear immunological issues.

The aim of the study was to access the SARS-CoV-2 antibody seroprevalence in healthcare workers (HCWs) of a tertiary pediatric hospital after the first wave of the pandemic and to compare the results among seven commercially available antibody detection assays, including chemiluminescence (CMIA), electroluminescence (ECLIA), Εnzyme-Linked Immunosorbent Assay (ELISA), and rapid immunochromatography (RIC). SARS-CoV-2 antibody detection was performed in serum samples of 1216 HCWs, using a reference CMIA assay and 8/1216 (0.66%) were detected positive. Positive serum samples were further tested with other assays; however, only one sample was positive by all tests. The rest 7 cases were negative with ECLIA and ELISA and gave discordant results with RIC test. Six months later, new serum samples of seropositive HCWs were analyzed with the same 7 tests, with inconsistent results again. Identification of reliable SARS-CoV-2 antibody tests is important to determine the actual number of past infections, the duration of antibodies, and guide public health decisions.

The persistence of symptoms for a long time after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is now familiar as post-COVID syndrome (PCS). To the best of our knowledge, the risk of long-term clinical outcomes in children after SARS-CoV-2 infection is still unclear. Unlike in adults, current evidence suggests a lower prevalence of persistent symptoms in children. However, since several studies are characterized by great heterogeneity, it is difficult to accurately estimate the exact incidence of PCS in children. The presence and course of recovery depend on risk factors that are more common in adults than children. Proposed pathophysiological mechanisms in PCS in children include age-dependent immune responses, angiotensin-converting enzyme 2 expression, blood-brain barrier development or social issues affecting children behavior, such as school closure and social isolation. However, further longitudinal studies are required for unanswered issues to be clarified. The aim of the present review is to describe the long-term symptoms per biological system in children, potential risk factors and the role of the immune system in the presence of PCS.

Although coronavirus disease 2019 (COVID-19) is mild in nearly all children, a small proportion of pediatric patients develop severe or critical illness. Guidance is therefore needed regarding use of agents with potential activity against severe acute respiratory syndrome coronavirus 2 in pediatrics.A panel of pediatric infectious diseases physicians and pharmacists from 18 geographically diverse North American institutions was convened. Through a series of teleconferences and web-based surveys, a set of guidance statements was developed and refined based on review of best available evidence and expert opinion.Given the typically mild course of pediatric COVID-19, supportive care alone is suggested for the overwhelming majority of cases. The panel suggests a decision-making framework for antiviral therapy that weighs risks and benefits based on disease severity as indicated by respiratory support needs, with consideration on a case-by-case basis of potential pediatric risk factors for disease progression. If an antiviral is used, the panel suggests remdesivir as the preferred agent. Hydroxychloroquine could be considered for patients who are not candidates for remdesivir or when remdesivir is not available. Antivirals should preferably be used as part of a clinical trial if available.Antiviral therapy for COVID-19 is not necessary for the great majority of pediatric patients. For those rare cases of severe or critical disease, this guidance offers an approach for decision-making regarding antivirals, informed by available data. As evidence continues to evolve rapidly, the need for updates to the guidance is anticipated.

The incidence and severity of coagulation abnormalities have not been extensively studied in pediatric populations with coronavirus disease 2019 (COVID-19). Moreover, their association with an increased risk for thromboembolic events remains unclear, and there is a lack of evidence for optimal prophylactic antithrombotic management. The aim of our study was to present our experience in evaluation, management, and long-term outcomes of coagulation abnormalities in pediatric hospitalized patients with COVID-19.A prospective study was performed in all children hospitalized for COVID-19 during a 6-month period focusing on patients' coagulation abnormalities, the normalization of the coagulation profile with or without anticoagulation prophylaxis and the clinical outcome of the disease.Two hundred twenty-three patients (median age: 11.4 months) were enrolled in the study. Coagulation abnormalities were detected in 92.4% of patients with increased D-dimer levels to be the most common abnormality detected in 84.3% of patients. Prophylactic anticoagulation was initiated only in 7 (3.1%) selected patients with severe COVID-19 and at least 2 risk factors for venous thromboembolism (VTE) and in all patients with previous history of VTE. Follow-up coagulation profile in 85 patients showed that changes over time had a tendency towards normalization irrespectively of the initiation of anticoagulant thromboprophylaxis. No thrombotic complications were observed 3 months upon discharge.Although abnormal findings in coagulation profile were very common, they were not associated with risk for VTE even in severe cases. A trend of normalization early in the course of the disease was observed regardless of the use of anticoagulant thromboprophylaxis.

BACKGROUND To evaluate the performance of serum amyloid-A (SAA), high-density lipoprotein cholesterol (HDL-C) and apolipoprotein-A1 (Apo-A1) levels in the identification and monitoring of neonatal sepsis. METHODS This prospective study included 113 full-term septic neonates (postnatal age 4-28 days) admitted to the Special Care Neonatal Unit of a University Hospital from January 1, 2016, to April 30, 2019, and 68 healthy neonates (controls). Blood samples were drawn serially in septic neonates at enrollment and on days 1, 3 and 7, and once in controls, for SAA, HDL-C and Apo-A1 determination. RESULTS At enrollment, SAA levels were significantly higher in septic neonates in comparison with controls (median 50.7 vs. 3.5 mg/L; P < 0.0001); HDL-C and Apo-A1 levels were significantly lower in patients than in controls (P < 0.001 and P < 0.006, respectively). SAA levels were higher in culture-positive compared with culture-negative sepsis (median 202.0 vs. 14.2 mg/L; P < 0.0001). HDL-C and Apo-A1 levels did not differ significantly between culture-positive and culture-negative sepsis. Receiver operating characteristic curve analysis of SAA levels at enrollment resulted in significant areas under the curve (AUC) for detecting sepsis {AUC = 0.929 [95% confidence interval: 0.885-0.973]; P < 0.0001} and also for discriminating between culture-positive and culture-negative sepsis [AUC = 0.933 (95% confidence interval: 0.882-0.984); P < 0.0001]. The combination of HDL-C and Apo-A1 with SAA increased its diagnostic performance. Furthermore, serial SAA levels following enrollment could indicate clinical response in septic neonates. CONCLUSIONS SAA seems to be a useful biomarker for identification and monitoring of neonatal sepsis, and also for discriminating between culture-positive and culture-negative sepsis. HDL-C and Apo-A1 could be used as complementary markers.

Thrombotic complications of SARS-CoV-2 have been increasingly recognized as an important component of COVID-19 in adults; however, they have been less evident in children. We report a case of a teenager with positive SARS‐CoV‐2 RT–PCR and underlying prothrombotic risk factors, including aromatase inhibitor therapy, who developed deep vein thrombosis resulting in pulmonary embolism. Laboratory tests revealed deranged coagulation parameters (high D-dimers and Factor VIII and low antithrombin). The patient required intensive care and was managed with anticoagulants, dexamethasone and antithrombin concentrate. Clinical condition and hemostatic profile gradually improved. A review of the available literature for similar cases is presented.

As Greece is a country which has introduced the 13-valent pneumococcal conjugate vaccine (PCV13) both in the infant and in the adult immunization programs, the aim of the study was to investigate age-specific and serotype-specific trends of pneumococcal meningitis over an 11-year period (2010-2020).Data are reported from pneumococcal meningitis cases [notified to the National Public Health Organization (NPHO)], with clinical samples and bacterial isolates sent for pneumococcal identification and serotyping at the National Meningitis Reference Laboratory (NMRL). Pneumococcal identification was performed directly on clinical samples or bacterial isolates by multiplex PCR (mPCR) assay, while serotyping was carried out by application of the Capsular Sequence Typing (CST) method with the combination of single tube PCR assays.A total of 427 pneumococcal meningitis cases were notified to the NPHO between 2010 and 2020. Among those, 405 (94.8%) were microbiologically confirmed, while samples from 273 patients were sent to the NMRL for identification and/or further typing. The annual notification rate peaked at 0.47/100,000 in 2016 and since then has been decreasing. The incidence was highest in infants and in older adults. Pneumococcal serotypes were identified in 260/273 (95.2%) cases, where clinical samples were sent to the NMRL. The most prevalent serotypes (≥5%) were 3, 19A, 23B, 15B/C, 11A/D, 23A, 22F. During the study period there has been a decrease of PCV13 serotypes combined with an increase of non-PCV13 serotypes (p = 0.0045).This is the first study to report serotypes for pneumococcal meningitis across all ages in the post-PCV13 era in Greece. There is a need to enhance surveillance, by close monitoring of the emerging serotypes and the impact of vaccination programs. Higher-valency PCVs may help to improve the coverage of pneumococcal disease.

Data regarding immunogenicity of SARS-CoV-2 BNT162b2 vaccine in cystic fibrosis (CF) patients are limited. We prospectively measured total (TAbs-RBD; U/ml) and neutralizing (NAbs-RBD; %) antibodies of SARS-CoV-2 spike-receptor binding domain (RBD) protein in 33 CF patients and 66 healthy controls with median age (IQR): 19.6 (17.6-24.3) years and 31 (29-36) years, respectively and investigated possible associations with epidemiological and clinical parameters. Compared to healthy controls, CF patients had higher levels of TAbs-RBD and NAbs-RBD after both doses (P-value 0.001). One month after the second dose, CF patients and controls had TAbs-RBD: median (IQR): 3396 (2443) and 1452 (1231) U/ml, respectively. Similarly, the NAbs-RBD (%) were: 97.30 (1.00) and 95.70 (3.71) %, respectively. CF patients also had fewer local and systemic adverse events (AEs) (P-value 0.001). Among CF patients, no significant differences in immunogenicity were detected regarding the phenotype, genotype, medications, or severity of the disease. BNT162b2 vaccine was immunogenic with limited reactogenicity in CF patients regardless of the phenotype or severity of disease.

Limited prospective serosurveillance data in children regarding severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have been reported. We prospectively investigated SARS-CoV-2 seropositivity in children during a 16-month period of the coronavirus disease 2019 (COVID-19) pandemic, including the four waves of the pandemic, before SARS-CoV-2 adolescents' vaccination. Serum samples from children admitted to the major tertiary Greek pediatric hospital for any cause, except for COVID-19 infection, were randomly collected from 05/2020 to 08/2021. The study period was divided into four 4-month periods representing relevant epidemic waves. Total SARS-CoV-2 antibodies for nucleocapsid protein were determined using the Elecsys® Anti-SARS-CoV-2 reagent. A total of 3099 children (0-16 years) were included in the study. A total of 344 (11.1%) seropositive children were detected (males: 205 [59.5%]; median age [interquartile range [IQR]]: 3 years [0.6-10]). Seropositivity rates (%) increased during the four 4-month periods: 1.4%, 8.6%, 17.2%, and 17.6%, respectively. A correlation of seropositivity rates in children with new diagnosed SARS-CoV-2 cases in the community was detected. No significant differences were detected between males and females. Seropositivity was significantly higher in hospitalized than in nonhospitalized children and in non-Greek compared to Greek children (p 0.001). The lowest seropositivity rate before school opening (9/2021) was detected in the age groups 6-12 years (14.4%) and 12-16 years (16.1%). However, compared with the other age groups, the lowest median antibody titers were observed in children 0-1 year (median [IQR]: 13.9 cut-off index: [4.5-53.9] [p 0.001]). Although the seropositivity of children was related to the community epidemic waves, the exposure was limited. Low seropositivity rates in school-age children support the need for SARS-CoV-2 immunization.

INTRODUCTION: The aim of the study was to investigate the prevalence and severity of adverse reactions (ARs) after immunization of healthcare workers (HCWs) with BNT162b2 vaccine and to associate them with clinical and epidemiological characteristics. METHODS: A form containing demographic and clinical data as well as ARs after both doses of the vaccine was completed, and statistical association analysis was performed. RESULTS: A total of 502 HCWs (females 78.3%) with mean age (±SD) 48.17 years (±12.97) participated. After the first dose, 404 (80.5%) HCWs reported at least one local AR (LAR) and 366 (72.9%) after the second dose (p-value=0.004). After the first dose, 121 (24.1%) HCWs reported at least one systemic AR (SAR) and 275 (54.8%) after the second dose (p-value

Thrombotic complications of SARS-CoV-2 have been increasingly recognized as an important component of COVID-19 in adults; however, they have been less evident in children. We report a case of a teenager with positive SARS‐CoV‐2 RT–PCR and underlying prothrombotic risk factors, including aromatase inhibitor therapy, who developed deep vein thrombosis resulting in pulmonary embolism. Laboratory tests revealed deranged coagulation parameters (high D-dimers and Factor VIII and low antithrombin). The patient required intensive care and was managed with anticoagulants, dexamethasone and antithrombin concentrate. Clinical condition and hemostatic profile gradually improved. A review of the available literature for similar cases is presented.

BACKGROUND: Data regarding the association of antibody levels elicited after immunization with the BNT162b2 mRNA COVID-19 vaccine with epidemiological and clinical parameters are limited. METHODS: We prospectively measured the total (TAbs-RBD) and the neutralizing antibodies (NAbs-RBD) against the receptor binding domain (RBD) of SARS-CoV-2 spike protein in a cohort of 268 Healthcare workers before immunization, 20 days after the 1st dose and 30 days after the 2nd dose of the BNT162b2 vaccine. A statistical analysis for possible association of antibodies' levels with epidemiological and clinical parameters was performed. RESULTS: The mean age (±SD) of the participants was 45.45 years (±11.93) (range: 24-70 years) and 211 (79.9%) were females. Statistically significant differences were detected regarding both TAbs-RBD and NAbs-RBD between the first and second doses of the vaccine (P 

Overweight and obesity in childhood and adolescence represent major public health problems of our century, and account for increased morbidity and mortality in adult life. Irisin and Fibroblast Growth Factor 21 (FGF-21) have been proposed as prognostic and/or diagnostic biomarkers in subjects with obesity and metabolic syndrome, because they increase earlier than other traditional biomarkers. We determined the concentrations of Irisin and FGF-21 in children and adolescents with overweight and obesity before and after one year of a life-style intervention program of diet and physical exercise and explored the impact of body mass index (BMI) reduction on the concentrations of Irisin, FGF-21 and other cardiometabolic risk factors. Three hundred and ten (n = 310) children and adolescents (mean age ± SD: 10.5 ± 2.9 years) were studied prospectively. Following one year of the life-style intervention program, there was a significant decrease in BMI (p = 0.001), waist-to-hip ratio (p = 0.024), waist-to-height ratio (p = 0.024), and Irisin concentrations (p = 0.001), and an improvement in cardiometabolic risk factors. There was no alteration in FGF-21 concentrations. These findings indicate that Irisin concentrations decreased significantly as a result of BMI reduction in children and adolescents with overweight and obesity. Further studies are required to investigate the potential role of Irisin as a biomarker for monitoring the response to lifestyle interventions and for predicting the development of cardiometabolic risk factors.