Saliva for molecular detection of SARS-CoV-2 in pre-school and school-age children.

SARS-CoV-2 diagnosis is a cornerstone for the management of coronavirus disease 2019 (COVID-19). Numerous studies have assessed saliva performance over nasopharyngeal sampling (NPS), but data in young children are still rare. We explored saliva performance for SARS-CoV-2 detection by RT-PCR according to the time interval from initial symptoms or patient serological status. We collected 509 NPS and saliva paired samples at initial diagnosis from 166 children under 12 years of age (including 57 children under 6), 106 between 12 and 17, and 237 adults. In children under 12, overall detection rate for SARS-CoV-2 was comparable in saliva and NPS, with an overall agreement of 89.8%. Saliva sensitivity was significantly lower than that of NPS (77.1% compared to 95.8%) in pre-school and school-age children but regained 96% when considering seronegative children only. This pattern was also observed to a lesser degree in adolescents but not in adults. Sensitivity of saliva was independent of symptoms, in contrary to NPS, whose sensitivity decreased significantly in asymptomatic subjects. Performance of saliva is excellent in children under 12 at early stages of infection. This reinforces saliva as a collection method for early and unbiased SARS-CoV-2 detection and a less invasive alternative for young children.

Multisystem inflammatory syndrome in children rose and fell with the first wave of the COVID-19 pandemic in France.

AIM: This study determined the influence of the COVID-19 pandemic on the occurrence of multisystem inflammatory syndrome in children (MIS-C) and compared the main characteristics of MIS-C and Kawasaki disease (KD). METHODS: We included patients aged up to 18 years of age who were diagnosed with MIS-C or KD in a paediatric university hospital in Paris from 1 January 2018 to 15 July 2020. Clinical, laboratory and imaging characteristics were compared, and new French COVID-19 cases were correlated with MIS-C cases in our hospital. RESULTS: There were seven children with MIS-C, from 6 months to 12 years of age, who were all positive for the virus that causes COVID-19, and 40 virus-negative children with KD. Their respective characteristics were as follows: under 5 years of age (14.3% vs. 85.0%), paediatric intensive care unit admission (100% vs. 10.0%), abdominal pain (71.4% vs. 12.5%), myocardial dysfunction (85.7% vs. 5.0%), shock syndrome (85.7% vs. 2.5%) and mean and standard deviation C-reactive protein (339 ± 131 vs. 153 ± 87). There was a strong lagged correlation between the rise and fall in MIS-C patients and COVID-19 cases. CONCLUSION: The rise and fall of COVID-19 first wave mirrored the MIS-C cases. There were important differences between MIS-C and KD.

Prior infection by seasonal coronaviruses, as assessed by serology, does not prevent SARS-CoV-2 infection and disease in children, France, April to June 2020.

BackgroundChildren have a low rate of COVID-19 and secondary severe multisystem inflammatory syndrome (MIS) but present a high prevalence of symptomatic seasonal coronavirus infections.AimWe tested if prior infections by seasonal coronaviruses (HCoV) NL63, HKU1, 229E or OC43 as assessed by serology, provide cross-protective immunity against SARS-CoV-2 infection.MethodsWe set a cross-sectional observational multicentric study in pauci- or asymptomatic children hospitalised in Paris during the first wave for reasons other than COVID (hospitalised children (HOS), n = 739) plus children presenting with MIS (n = 36). SARS-CoV-2 antibodies directed against the nucleoprotein (N) and S1 and S2 domains of the spike (S) proteins were monitored by an in-house luciferase immunoprecipitation system assay. We randomly selected 69 SARS-CoV-2-seropositive patients (including 15 with MIS) and 115 matched SARS-CoV-2-seronegative patients (controls (CTL)). We measured antibodies against SARS-CoV-2 and HCoV as evidence for prior corresponding infections and assessed if SARS-CoV-2 prevalence of infection and levels of antibody responses were shaped by prior seasonal coronavirus infections.ResultsPrevalence of HCoV infections were similar in HOS, MIS and CTL groups. Antibody levels against HCoV were not significantly different in the three groups and were not related to the level of SARS-CoV-2 antibodies in the HOS and MIS groups. SARS-CoV-2 antibody profiles were different between HOS and MIS children.ConclusionPrior infection by seasonal coronaviruses, as assessed by serology, does not interfere with SARS-CoV-2 infection and related MIS in children.

Association of Intravenous Immunoglobulins Plus Methylprednisolone vs Immunoglobulins Alone With Course of Fever in Multisystem Inflammatory Syndrome in Children.

Importance: Multisystem inflammatory syndrome in children (MIS-C) is the most severe pediatric disease associated with severe acute respiratory syndrome coronavirus 2 infection, potentially life-threatening, but the optimal therapeutic strategy remains unknown. Objective: To compare intravenous immunoglobulins (IVIG) plus methylprednisolone vs IVIG alone as initial therapy in MIS-C. Design, Setting, and Participants: Retrospective cohort study drawn from a national surveillance system with propensity score-matched analysis. All cases with suspected MIS-C were reported to the French National Public Health Agency. Confirmed MIS-C cases fulfilling the World Health Organization definition were included. The study started on April 1, 2020, and follow-up ended on January 6, 2021. Exposures: IVIG and methylprednisolone vs IVIG alone. Main Outcomes and Measures: The primary outcome was persistence of fever 2 days after the introduction of initial therapy or recrudescence of fever within 7 days, which defined treatment failure. Secondary outcomes included a second-line therapy, hemodynamic support, acute left ventricular dysfunction after first-line therapy, and length of stay in the pediatric intensive care unit. The primary analysis involved propensity score matching with a minimum caliper of 0.1. Results: Among 181 children with suspected MIS-C, 111 fulfilled the World Health Organization definition (58 females [52%]; median age, 8.6 years [interquartile range, 4.7 to 12.1]). Five children did not receive either treatment. Overall, 3 of 34 children (9%) in the IVIG and methylprednisolone group and 37 of 72 (51%) in the IVIG alone group did not respond to treatment. Treatment with IVIG and methylprednisolone vs IVIG alone was associated with lower risk of treatment failure (absolute risk difference, -0.28 [95% CI, -0.48 to -0.08]; odds ratio [OR], 0.25 [95% CI, 0.09 to 0.70]; P = .008). IVIG and methylprednisolone therapy vs IVIG alone was also significantly associated with lower risk of use of second-line therapy (absolute risk difference, -0.22 [95% CI, -0.40 to -0.04]; OR, 0.19 [95% CI, 0.06 to 0.61]; P = .004), hemodynamic support (absolute risk difference, -0.17 [95% CI, -0.34 to -0.004]; OR, 0.21 [95% CI, 0.06 to 0.76]), acute left ventricular dysfunction occurring after initial therapy (absolute risk difference, -0.18 [95% CI, -0.35 to -0.01]; OR, 0.20 [95% CI, 0.06 to 0.66]), and duration of stay in the pediatric intensive care unit (median, 4 vs 6 days; difference in days, -2.4 [95% CI, -4.0 to -0.7]). Conclusions and Relevance: Among children with MIS-C, treatment with IVIG and methylprednisolone vs IVIG alone was associated with a more favorable fever course. Study interpretation is limited by the observational design.

Cardiac MRI in Children with Multisystem Inflammatory Syndrome Associated with COVID-19.

This case series examines cardiac MRI findings in four children and adolescents admitted to intensive care in April 2020 for multisystem inflammatory syndrome and Kawasaki disease-like features related to coronavirus disease 2019 (COVID-19). Acute myocarditis occurred less than 1 week after onset of fever and gastrointestinal symptoms. Physical examination showed rash and cheilitis or conjunctivitis. All patients recovered after intravenous immunoglobulin therapy. Severe acute respiratory syndrome coronavirus 2 reverse transcription polymerase chain reaction was negative in nasopharyngeal, stool, and respiratory samples and was positive on serology. Cardiac MRI showed diffuse myocardial edema on T2 short tau inversion-recovery sequences and native T1 mapping, with no evidence of late gadolinium enhancement suggestive of replacement fibrosis or focal necrosis. These findings favor postinfectious myocarditis in children and adolescents with COVID-19.

Bone and joint infections in infants under three months of age.

AIM: Studies on bone and joint infections (BJI) in infants under three months are rare. We described the clinical and paraclinical features and outcomes of infants hospitalised with BJI under three months of age. METHODS: The French National Hospital Discharge Database provided data on BJIs in infants under three months of age from January 2004 to 2015 in three Parisian Paediatric teaching hospitals. RESULTS: We included 71 infants under three months of age with BJI, the median age was 25 days, and the interquartile range (IQR) was 17-43 days. The most common infection sites were the hip (32%) and knee (32%). Symptoms included pain (94%), limited mobility (87%) and/or fever (52%). There were 11 (15.5%) cases of nosocomial BJI. A pathogen was identified in 51 infants (71.8%), including Streptococcus agalactiae (45%), Staphylococcus aureus (22%) and Escherichia coli (18%). The initial median C-reactive protein test rate was 31 mg/L (IQR 17-68). Of the 34 infants followed for more than one year, four developed severe orthopaedic conditions such as epiphysiodesis, limb length discrepancy, bone necrosis and/or impaired limb function. CONCLUSION: Streptococcus agalactiae was the most common cause of BJI in infants under three months. Orthopaedic sequelae were rare, but severe, and required long-term follow-up.

Population Pharmacokinetics of Cefotaxime and Dosage Recommendations in Children with Sickle Cell Disease.

The pharmacokinetic profile of most drugs is dependent on the patient's covariates and may be influenced by the disease. Cefotaxime is frequently prescribed in pediatric patients with sickle cell disease (SCD), characterized by vaso-occlusive complications, chronic hemolytic anemia, and a defective immunological function predisposing the individual to severe infection. Data on the impact of the disease on the disposition of cefotaxime are missing. In the present study, our aims were to determine cefotaxime pharmacokinetics when prescribed to children with SCD for suspected or proven bacterial infection, identify significant covariates, and perform Monte Carlo simulations to optimize the drug dosage. Cefotaxime serum concentrations were measured in 78 pediatric SCD patients receiving cefotaxime intravenously at a daily dose of 200 mg/kg of body weight in three or four divided doses over 30 min. A total of 107 concentrations were available for pharmacokinetic analysis. A population pharmacokinetic model was developed with NONMEM software and used for Monte Carlo simulations. Cefotaxime concentrations ranged from 0.05 to 103.7 mg/liter. Cefotaxime pharmacokinetics were best described by a one-compartment model: the median estimated weight-normalized volume of distribution and clearance were 0.42 liter/kg (range, 0.2 to 1.1 liter/kg) and 0.38 liter/h/kg (range, 0.1 to 1.2 liter/h/kg). Cefotaxime clearance increased by 22% in patients with acute chest syndrome. Dosing optimization, performed using EUCAST MIC susceptibility breakpoints, showed that a dose of 100 mg/kg/6 h should be used, depending on the patient's characteristics and clinical presentation, in order to reach a value of the percentage of time that the drug concentration exceeded the MIC under steady-state pharmacokinetic conditions of 80% in 80% of the patients when targeting sensitive Gram-positive cocci and Gram-negative bacilli with MICs of 1 mg/liter or below.

Invasive pneumococcal disease in children can reveal a primary immunodeficiency.

BACKGROUND: About 10% of pediatric patients with invasive pneumococcal disease (IPD) die from the disease. Some primary immunodeficiencies (PIDs) are known to confer predisposition to IPD. However, a systematic search for these PIDs has never been carried out in children presenting with IPD. METHODS: We prospectively identified pediatric cases of IPD requiring hospitalization between 2005 and 2011 in 28 pediatric wards throughout France. IPD was defined as a positive pneumococcal culture, polymerase chain reaction result, and/or soluble antigen detection at a normally sterile site. The immunological assessment included abdominal ultrasound, whole-blood counts and smears, determinations of plasma immunoglobulin and complement levels, and the evaluation of proinflammatory cytokines. RESULTS: We included 163 children with IPD (male-to-female ratio, 1.3; median age, 13 months). Seventeen children had recurrent IPD. Meningitis was the most frequent type of infection (87%); other infections included pleuropneumonitis, isolated bloodstream infection, osteomyelitis, endocarditis, and mastoiditis. One patient with recurrent meningitis had a congenital cerebrospinal fluid fistula. The results of immunological explorations were abnormal in 26 children (16%), and a PID was identified in 17 patients (10%), including 1 case of MyD88 deficiency, 3 of complement fraction C2 or C3 deficiencies, 1 of isolated congenital asplenia, and 2 of Bruton disease (X-linked agammaglobulinemia). The proportion of PIDs was much higher in children aged >2 years than in younger children (26% vs 3%; P < .001). CONCLUSIONS: Children with IPD should undergo immunological investigations, particularly those aged >2 years, as PIDs may be discovered in up to 26% of cases.

Fluoroquinolones in pediatrics: review of hospital prescription use over 2 years.

OBJECTIVE: Numerous studies have shown that the tolerance of children to fluoroquinolones (FQs) is satisfactory, and some indications have been recently agreed upon. However, vigilance is required when prescribing FQ to children. The aim of our study was to describe the prescription of FQs to children hospitalized in our hospital. MATERIALS AND METHODS: This is a chart retrospective observational study at the Robert-Debré teaching Hospital between January 2009 and December 2010. Data was collected about patients (name, sex, weight, age) and prescribed treatments (indication, international nonproprietary names, dose, number of doses per day, administration route). Quality of collected data was assessed by analyzing the clinical files of 32 randomly selected patients. RESULTS: We analyzed data for 397 patients (3 days - 18 years old and 640 g - 115 kg). Ciprofloxacin was prescribed for 382 patients (96%), ofloxacin for 10 patients (3%), and levofloxacin for 5 patients (1%). Febrile neutropenia was the most common indication (108 patients, i.e., 27%), followed by inflammatory bowel disease (50 patients, 13%). Doses conformed to recommendations for 88% of the patients. Analysis of the 32 cases indicated an overall compliance percentage of 94.4%. CONCLUSION: This is the first study to collect so much data on FQ prescriptions for hospitalized children. Use in practice went beyond the licensed indication. Doses were consistent with those for recommended indications.

Pediatric gastroenteritis in the emergency department: practice evaluation in Belgium, France, The Netherlands and Switzerland.

BACKGROUND: Based on European recommendations of ESPGHAN/ESPID from 2008, first line therapy for dehydration caused by acute gastroenteritis (AGE) is oral rehydration solution (ORS). In case of oral route failure, nasogastric tube enteral rehydration is as efficient as intra-venous rehydration and seems to lead to fewer adverse events. The primary objective was to describe rehydration strategies used in cases of AGE in pediatric emergency departments (PEDs) in Belgium, France, The Netherlands, and Switzerland. METHODS: An electronic survey describing a scenario in which a toddler had moderate dehydration caused by AGE was sent to physicians working in pediatric emergency departments. Analytical data were analyzed with descriptive statistics and Kruskal -Wallis Rank test. RESULTS: We analyzed 68 responses, distributed as follows: Belgium N = 10, France N = 37, The Netherlands N = 7, and Switzerland N = 14. Oral rehydration with ORS was the first line of treatment for 90% of the respondents. In case of first line treatment failure, intravenous rehydration was preferred by 95% of respondents from France, whereas nasogastric route was more likely to be used by those from Belgium (80%), The Netherlands (100%) and Switzerland (86%). Serum electrolyte measurements were more frequently prescribed in France (92%) and Belgium (80%) than in The Netherlands (43%) and Switzerland (29%). Racecadotril was more frequently used in France, and ondansetron was more frequently used in Switzerland. No respondent suggested routine use of antibiotics. CONCLUSION: We found variations in practices in terms of invasiveness and testing. Our study supports the need for further evaluation and implementation strategies of ESPGHAN/ESPID guidelines. We plan to extend the study throughout Europe with support of the Young ESPID Group.

Salvage strategy for long-term central venous catheter-associated Staphylococcus aureus infections in children: a multicenter retrospective study in France.

OBJECTIVES: Catheter removal is recommended in adults with S. aureus central line-associated bloodstream infection (CLABSI) but is controversial in children with long-term central venous catheters (LTCVC). We evaluated the occurrence of catheter salvage strategy (CSS) in children with S. aureus LTCVC-associated CLABSI and assessed determinants of CSS failure. METHODS: We retrospectively included children (<18 years) with an LTCVC and hospitalized with S. aureus CLABSI in 8 French tertiary care hospitals (2010-2018). CSS was defined as an LTCVC left in place ≥ 72 hours after initiating empiric antibiotic treatment for suspected bacteremia. Characteristics of patients were reviewed, and multivariable logistic regression was performed to identify factors associated with CSS failure (i.e., persistence, recurrence, or complications of bacteremia). RESULTS: We included 273 episodes of S. aureus LTCVC-associated CLABSI. CSS was chosen in 194 out of 273 (71%) cases and failed in 74 of them (38%). The main type of CSS failure was the persistence of bacteremia (39 out of 74 cases, 53%). Factors independently associated with CSS failure were: history of catheter infection (adjusted odds ratio [aOR] 3.18, 95% confidence interval [95%CI] 1.38-7.36), CLABSI occurring on an implantable venous access device (aOR 7.61, 95%CI 1.98-29.20) when compared with tunneled-cuffed CVC, polymicrobial CLABSI (aOR 3.45, 95%CI 1.25-9.50), and severe sepsis at the initial stage of infection (aOR 4.46, 95%CI 1.18-16.82). CONCLUSIONS: CSS was frequently chosen in children with S. aureus LTCVC-associated CLABSI, and failure occurred in one-third of cases. The identified risk factors may help clinicians identify children at risk for CSS failure.

Two atypical cases of Kingella kingae invasive infection with concomitant human rhinovirus infection.

We describe two atypical cases of Kingella kingae infection in children diagnosed by PCR, one case involving a soft tissue abscess and one case a femoral Brodie abscess. Both patients had concomitant human rhinovirus infection. K. kingae strains, isolated from an oropharyngeal swab, were characterized by multilocus sequence typing and rtxA sequencing.

Treatment of Resistant Gram-negative bacilli in children.

Resistance of Gram-negative bacteria to the most widely used antibiotics, particularly ß-lactams, is now considered as major public health problem. The main resistance mechanisms to ß-lactams in Enterobacterales are the production of extended spectrum ß-lactamases (ESBL) or carbapenemases, which hydrolyze virtually all ß-lactams. However, a substantial proportion of carbapenem-resistant Gram-negative bacilli do not produce carbapenemase but combine overproduction of a cephalosporinase and/or ESBL with very low penem hydrolysis and reduced outer membrane permeability. The arrival of new antibacterial agents active on some of these multidrug-resistant strains, such as new ß-lactam inhibitors, has marked a turning point in treatment and represents real progress. In-depth knowledge of resistance mechanisms is crucial to the choice of the most effective molecule, and their prescription requires close collaboration between microbiologists, infectious disease specialists and intensive care physicians. While these compounds are significantly more active against resistant strains than those previously available, their spectrum of activity does not cover all resistance mechanisms in Gram-negatives, nor in other bacterial species potentially involved in polymicrobial infections. The use of these new compounds does not alter antibiotic regimens in terms of duration and indication of combined antibiotic therapy, which remain very limited.

Antimicrobial treatment of skin and soft tissue infections.

Bacterial skin infections are common in children, and frequently do not require systemic antibiotic therapy, particularly for superficial forms. In these cases, washing (with soap and water) and careful rinsing of the lesion are the key points of treatment. A semiotic analysis must precede any therapeutic decision to assess the appropriateness of antibiotic therapy, need for drainage (which may be spontaneous or surgical) and possible existence of symptoms related to toxin production, which are frequent signs of severity. The bacterial species most frequently implicated in children are Staphylococcus aureus and Streptococcus pyogenes. Given the low incidence of methicillin-resistant S. aureus in France (<10%), the first-line antibiotic treatment is amoxicillin-clavulanate, to which an anti-toxin treatment such as clindamycin may be added for patients with overt toxin signs.

Antibiotic therapy for osteoarticular infections in 2023: Proposals from the Pediatric Infectious Pathology Group (GPIP).

Most osteoarticular infections (OAI) occur via the hematogenous route, affect children under 5 years of age old, and include osteomyelitis, septic arthritis, osteoarthritis and spondylodiscitis. Early diagnosis and prompt treatment are needed to avoid complications. Children with suspected OAI should be hospitalized at the start of therapy. Surgical drainage is indicated in patients with septic arthritis or periosteal abscess. Staphylococcus aureus is implicated in OAI in children at all ages; Kingella kingae is a very common causative pathogen in children from 6 months to 4 years old. The French Pediatric Infectious Disease Group recommends empirical antibiotic therapy with appropriate coverage against methicillin-sensitive S. aureus (MSSA) with high doses (150 mg/kg/d) of intravenous cefazolin. In most children presenting uncomplicated OAI with favorable outcome (disappearance of fever and pain), short intravenous antibiotic therapy during 3 days can be followed by oral therapy. In the absence of bacteriological identification, oral relay is carried out with the amoxicillin/clavulanate combination (80 mg/kg/d of amoxicillin) or cefalexin (150 mg/kg/d). If the bacterial species is identified, antibiotic therapy will be adapted to antibiotic susceptibility. The minimum total duration of antibiotic therapy should be 14 days for septic arthritis, 3 weeks for osteomyelitis and 4-6 weeks for OAI of the pelvis, spondylodiscitis and more severe OAI, and those evolving slowly under treatment or with an underlying medical condition (neonate, infant under 3 months of old, immunocompromised patients). Treatment of spondylodiscitis and severe OAI requires systematic orthopedic advice.

Factors influencing neurological outcome of children with bacterial meningitis at the emergency department.

We performed a cohort study of children who survived bacterial meningitis after the neonatal period at a single pediatric center in France over a 10-year period (1995-2004) to identify predictors of death and long-term neurological deficits in children with bacterial meningitis. We performed multivariate regression to determine independent predictors of death and neurologic deficits. We identified 101 children with bacterial meningitis of which 19 died during initial hospitalization. Need for mechanical ventilation [hazard ratio (HR) 11.5, 95 % confidence interval (CI) 2.4-55.5)] and thrombocytopenia defined as a platelet count <150 × 10(9) per liter (HR 0.6, 95 % CI 0.4-0.9) at presentation were associated with death during initial hospitalization. At final assessment, 42 of the 70 survivors had no neurologic deficits identified; 20 had a single deficit, and eight had multiple deficits. A delay in initiation of antibiotics (HR 1.3, 95 % CI 1.1-1.7) and hydrocephalus on computed tomographic scan (HR 2.6, 95 % CI 1.1-6.0) were associated with having one or more long-term neurologic deficits. Identification of children at risk of death or long-term neurologic sequelae may allow therapeutic interventions to be directed to children at the highest risk.

[Epidemiology and the burden of RSV]. / Épidémiologie et fardeau du VRS.

RSV is an almost obligatory virus responsible for upper (rhinitis and otitis) and lower (bronchiolitis and asthma attack) respiratory infections in children under 5 years of age. Reinfections are frequent at all ages because immunity is only partial and does not last long. Young children under the age of 1 are the most affected. The majority of these children are healthy. Having a risk factor (premature birth, heart disease, bronchopulmonary dysplasia, but also passive smoking) increases the severity of RSV pathology. Very few children currently benefit from prevention by anti-RSV monoclonal antibodies. The annual cost of care, the various socio-economic costs are a public health reality in three care sectors: out-patient, pediatric emergencies, hospitalization. Subsequent consequences: repeated wheezing and asthma, should also be taken into consideration and integrated into public health decisions. Progress in recognizing this pathology is desirable: distribution of diagnostic tests in the city; providing parents with information.

Le VRS est un virus quasi obligatoire responsable d'infections respiratoires hautes (rhinite et otite) et basses (bronchiolite et crise d'asthme) chez l'enfant de moins de 5 ans. Les réinfections sont fréquentes du fait d'une immunité partielle, peu durable, à tous les âges de la vie. Les jeunes enfants de moins de 1 an sont les plus touchés. La majorité de ces enfants sont bien portants. Avoir un facteur de risque (prématurité, cardiopathie, dysplasie bronchopulmonaire mais aussi tabagisme passif) majore la sévérité de la pathologie à VRS. Très peu d'enfants bénéficient actuellement d'une prévention par les anticorps monoclonaux anti-VRS. La charge annuelle en soins, les coûts socioéconomiques variés constituent une réalité de santé publique portant sur les trois secteurs de soins : ambulatoire, urgences pédiatriques, hospitalisation.Les conséquences ultérieures : répétition de wheezing, asthme, devraient aussi être pris en considération et intégrés dans les décisions de santé publique.Des progrès dans la reconnaissance de cette pathologie sont souhaitables : diffusion des tests diagnostiques en ville ; information aux parents.

Retrospective observational study of the influence of the COVID-19 outbreak on infants' hospitalisation for acute bronchiolitis.

OBJECTIVES: Acute bronchiolitis is a major public health issue with high number of infants hospitalised worldwide each year. In France, hospitalisations mostly occur between October and March and peak in December. A reduction of emergency visits for bronchiolitis has been observed at onset of the COVID-19 outbreak. We aimed to assess the pandemic effects on the hospitalisations for bronchiolitis during the 2020-2021 winter (COVID-19 period) compared with three previous winters (pre-COVID-19). DESIGN: Retrospective, observational and cross-sectional study. SETTING: Tertiary university paediatric hospital in Paris (France). PARTICIPANTS: All infants aged under 12 months who were hospitalised for acute bronchiolitis during the autumn/winter seasons (1 October to 31 March) from 2017 to 2021 were included. Clinical and laboratory data were collected using standardised forms. RESULTS: During the COVID-19 period was observed, a 54.3% reduction in hospitalisations for bronchiolitis associated with a delayed peak (February instead of November-December). Clinical characteristics and hospitalisation courses were substantially similar. The differences during the COVID-19 period were: smaller proportion of infants with comorbidities (8% vs 14% p=0.02), lower need for oxygen (45% vs 55%, p=0.01), higher proportions of metapneumovirus, parainfluenzae 3, bocavirus, coronavirus NL63 and OC43 (all p≤0.01) and no influenza. The three infants positive for SARS-CoV-2 were also positive for respiratory syncytial virus, suggesting that SARS-CoV-2 alone does not cause bronchiolitis, despite previous assumptions. CONCLUSION: The dramatic reduction in infants' hospitalisations for acute bronchiolitis is an opportunity to change our future habits such as advising the population to wear masks and apply additional hygiene measures in case of respiratory tract infections. This may change the worldwide bronchiolitis burden and improve children respiratory outcomes.