An observational study in Children <24 Months Hospitalized for RSV-related Lower Respiratory Tract Infection, sponsored by Assistance Publique - Hôpitaux de Paris. Not yet recruiting at 1 site in France. Open to participants aged Up to 24 Months. Per ClinicalTrials.gov, last updated 2026-10-26.
Sponsored by Assistance Publique - Hôpitaux de Paris · Observational
Hospitalization for RSV lower respiratory tract infections (LRTI) still occurs, including in infants having received nirsevimab/clesrovimab or born to mothers vaccinated with Abrysvo.
We hypothesize that pediatric patients hospitalized for RSV LRTIs occurring in the era of large use of prophylaxis, could be, at least in part, explained by virological factors (emergence/selection of variants with decreased susceptibility to prophylaxis) and/or immunological factors (inherited immune deficiency, presence of auto-antibodies neutralizing anti-viral cytokines such as type I interferons, impaired mucosal responses or mucosal pharmacokinetics issues inducing low levels of local concentrations of nirsevimab/clesrovimab).
In this cohort study, all paediatric patients hospitalized for severe RSV infection will be included at the time of hospitalization.
We aim to detect virological variants with decreased sensitivity to the prophylaxis previously administered (Abrysvo and/or nirsevimab/clesrovimab) will be performed by sequencing the full-length RSV genome to detect any polymorphisms and/or resistance associated mutations in the F protein.
Nasal swabs, salivary and blood samples will be collected at inclusion. Those hospitalized for ≥ 5 days will undergo another nasopharyngeal sample at day 7 +/-2 of hospitalization. Two groups of patients will be identified according to their exposure or non-exposure to prophylaxis.
Briefly:
302 studies on the registry are indexed under Respiratory Syncytial Virus Infections; 48 are open to participants now.
This study's planned enrollment of 300 is below the median of 350 across 76 observational studies indexed under Respiratory Syncytial Virus Infections.
Browse Respiratory Syncytial Virus Infections studies →Assistance Publique - Hôpitaux de Paris is the lead sponsor of 3,578 studies on the registry; 1,030 are open to participants now.
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Pediatric patients hospitalized for RSV LRTI
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Child \< 24 months admitted to the hospital for RSV-related lower respiratory tract infection (LRTI)
Biological: Prior exposure to prophylactic treatment with Abrysvo or nirsevimab/clesrovimab · Biological: Non-exposure to prior prophylactic treatment
Being born to a woman having received Abrysvo vaccine ≥ 14 days before delivery (thus, children born to mothers vaccinated \<14 days before delivery will be considered as "unexposed" to Abrysvo) AND being less than 12 months of age at the time of admission for RSV LRTI OR having received nirsevimab or clesrovimab ≥ 7 days and \< 12 months before admission for RSV LRTI (thus, children admitted \< 7 days after nirsevimab/clesrovimab administration will be considered as "unexposed" to nirsevimab/clesrovimab).
all other children will be considered as non-exposed to prophylaxis
RSV variants with reduced sensitivity to prophylaxis
Detection of virological variants with decreased sensitivity to the prophylaxis previously administered (nirsevimab/clesrovimab and/or Abrysvo), performed by sequencing the full-length RSV genome to detect any polymorphisms and/or resistance associated mutations in the F protein
Time frame: Day0/At inclusion
RSV variants with reduced sensitivity to nirsevimab/clesrovimab according to age at hospitalization
Detection among children exposed to nirsevimab/clesrovimab before 12 months of age and assessment of RSV harboring polymorphisms or resistance-associated substitutions conferring decreased susceptibility to nirsevimab/clesrovimab in those hospitalized for RSV LRTI during their 1st year of life versus those hospitalized during their 2nd year of life
Time frame: Day 0
Immunological characteristics of children hospitalized with RSV LRTI
Detection of the following immunological characteristics: * identification of a primary immune deficiency (previously undiagnosed in the participants), by whole exome sequencing * detection of auto-antibodies neutralizing type I IFNs in serum, by a luciferase reporter assay and multiplex detection assays
Time frame: Day 0
Mucosal immunity of children hospitalized with RSV LRTI
Assessment of mucosal immunity (detection in saliva swabs of IgG or SIgA anti-RSV response (protein F), and correlation with functional neutralizing anti-RSV responses (RSV A and B strain))
Time frame: Day 0
Viral kinetics
Evaluation of the kinetics of RSV RNA in nasal swab at inclusion and day 7+/-2 (for patients still hospitalized), using qPCR
Time frame: Day 0 and 7 +/-2 days
Plan to share: No
No publications or documents are linked to this record.
Start is estimated for Nov 2026; primary completion for Nov 2028, 24 months later.
Of 32 observational studies under Respiratory Syncytial Virus Infections, half reached primary completion within 25 months of starting (the median), counting those still running; a quarter within 11 and three quarters within 51. This study's planned 24 months is close to that.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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