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Table 3 Key Variables and Sources of Information for Hospitalized and Non-Ill Infants

From: Influenza and respiratory syncytial virus in infants study (IRIS) of hospitalized and non-ill infants aged <1 year in four countries: study design and methods

  Hospitalized Infants Non-Ill Infants
Enrollment 3–5 Week Follow-Up Hospital Records Enrollment
 Combined nasal and oropharyngeal swabs   
 Blood (Sera)   
 Endotracheal aspirate (for intubated infants)    
Infant illness
 Date of illness onset and resolution   
 Maternal-reported symptoms   
 Ambulatory and self-care for illness   
 Clinical signs at admission and per day    
 Clinical diagnoses    
 Clinical interventions    
 Clinical laboratory results    
 Clinical radiographic information    
 Readmission to hospital   
 Other hospitalizations post-discharge   
Infant characteristics
 Demographic (sex, birth date, race, ethnicity) information   
 Current weight
 Current length
 Perceived overall health and functioning  
 Influenza vaccination status (from vaccination cards when available)
 Delivery characteristics (including gestational age, birth weight, complications and abnormalities)  
 Diagnoses and history of care for chronic conditions  
 Diagnoses and history of care for prior acute illnesses  
 Results of previous laboratory tests    
 Other immunization status
 Daycare attendance   
Household characteristics
 Age of each household member   
 Education and occupation of parents (or guardians)   
 House size and number of rooms   
 Subjective social status   
 Household wealth index   
 Household smoking   
Maternal characteristics
 Subjective health status  
 Medical conditions   
 Pregnancy history and complications during study infant’s gestation   
 History of and current breastfeeding   
 Influenza vaccination status (from vaccination cards when available)
 Knowledge of and worry about influenza illness   
 Knowledge of and attitudes toward influenza vaccine for infants aged ≥6 months