TARSILA Real-World Evidence Study

Tarsila Inpatient Study Inclusion Criteria * Infant born in Brazil. * Mother resident in Brazil during the related pregnancy. * Infant date of birth 14 days or more after start of the first national RSVpreF vaccination campaign to ensure potential to have been born to an RSVpreF-vaccinated mother. * Infant ≤360 days of age at time of RSV specimen collection. * Infant born at ≥37 weeks of gestational age. * Infant hospital admission for at least 24 hours with signs and symptoms meeting the case definition of ARI, defined as the presence of any of the following: nasal secretion for ≥24 hours; respiratory distress, labored breathing, or tachypnea (respiratory rate ≥60 breaths/min for infants \<2 months or ≥50 breaths/min for infants 2-12 months); cough; inability to feed for any period due to respiratory symptoms; apnea; or other relevant respiratory symptoms (examples include but are not limited to wheezing, crackles, and nasal flaring). Exclusion Criteria: * Maternal or infant receipt of any other licensed or investigational RSV preventive product. * Infant receipt of blood transfusion or other blood products containing antibodies since birth. * Infant previously enrolled in this study. * Lack of informed consent from the mother or the infant's legal guardian. * Absent or inconclusive RT-qPCR result for RSV. * Birth to a mother whose RSVpreF vaccination status could not be confirmed. Tarsila Outpatient Study Inclusion Criteria: * Infant born in Brazil. * Mother resident in Brazil during the related pregnancy. * Infant date of birth 14 days or more after start of the first national RSVpreF vaccination campaign to ensure potential to have been born to an RSVpreF-vaccinated mother. * Infant ≤360 days of age at time of RSV specimen collection. * Infant born at ≥37 weeks of gestational age. * Infant presentation to an outpatient healthcare facility with signs and symptoms meeting the case definition of ARI, defined as the presence of any of the following: nasal secretion for ≥24 hours; respiratory distress, labored breathing, or tachypnea (respiratory rate ≥60 breaths/min for infants \<2 months or ≥50 breaths/min for infants 2-12 months); cough; inability to feed for any period due to respiratory symptoms; apnea; or other relevant respiratory symptoms (examples include but are not limited to wheezing, crackles, and nasal flaring). Exclusion Criteria: * Mother or infant receipt of any other licensed or investigational RSV preventive product. * Infant receipt of blood transfusion or other blood products containing antibodies since birth. * Lack of informed consent from the mother or the infant's legal guardian. * Absent or inconclusive RT-qPCR result for RSV. * Birth to a mother whose RSVpreF vaccination status could not be confirmed. * Enrollment in the study within the previous 30 days. If the interval exceeds 30 days, infants will be excluded if any previous episode tested positive for RSV.