TARSILA Real-World Evidence Study (TARSILA)

Real-world Effectiveness of maTernAl RSVpreF vaccInation Against RSV-associated Acute Respiratory ilLness in Infants in BrAzil (TARSILA Study): a Multicentre, Prospective, Test-negative, Case-Control Study

The overall objective of Tarsila Study is to estimate the real-world vaccine effectiveness of maternal RSVpreF immunization during pregnancy in Brazil against medically attended (inpatient and outpatient) respiratory syncytial virus-associated acute respiratory illness in infants. To achieve this, two multicenter, prospective, test-negative case-control studies will be conducted among infants with ARI: the TARSILA Inpatient Study, evaluating hospitalized infants and the TARSILA Outpatient Study, evaluating infants managed in outpatient settings.

Study Overview

• Status: Not yet recruiting
• Conditions: Respiratory Syncytial Virus (RSV); Lower Respiratory Tract Disease; Maternal Immunization; Infant Outcomes; Acute Respiratory Illness (ARI)
• Intervention / Treatment: Biological: respiratory syncytial virus bivalent prefusion F vaccine

Detailed Description

Tarsila comprises two multicenter, prospective, case-control studies using a test-negative design in Southern Brazil (states of Rio Grande do Sul, Santa Catarina, and Paraná). The Tarsila Inpatient study will enroll infants hospitalized due to acute respiratory illness and will be conducted at referral hospitals. The Tarsila Outpatient study will enroll infants with acute respiratory illness managed in outpatient settings and will be conducted at outpatient healthcare facilities. Both studies are aligned with the nationwide introduction of maternal RSVpreF vaccination in December 2025, with enrollment occurring from April, 2026 to September, 2028. In both studies, the same clinical case definition will be applied to cases and controls. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) for RSV will be prospectively performed to classify case infants (RT-qPCR positive for RSV) and control infants (RT-qPCR negative for RSV). Maternal RSVpreF vaccination status and potential confounders will be assessed through structured interviews and review of medical records.

• Study Type: Observational
• Enrollment (Estimated): 5000

Contacts and Locations

• Study Contact: Name: Maicon Falavigna, MD PhD; Phone Number: +55 51 2399 1750; Email: maicon@inovamedical.com.br

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Infants with acute respiratory illness (ARI)

Description

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.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Cases; Infants with a positive respiratory syncytial virus result on a nasal swab specimen	Biological: respiratory syncytial virus bivalent prefusion F vaccine; For both studies, the primary exposure is maternal receipt of respiratory syncytial virus bivalent prefusion F vaccination during pregnancy in accordance with the Brazilian National Immunization Program recommendation (24⁺⁰/₇ to 36⁺⁶/₇ weeks' gestation) with the receipt of the vaccine 14 days or more before delivery.
Controls; Infants with a negative respiratory syncytial virus result on a nasal swab specimen	Biological: respiratory syncytial virus bivalent prefusion F vaccine; For both studies, the primary exposure is maternal receipt of respiratory syncytial virus bivalent prefusion F vaccination during pregnancy in accordance with the Brazilian National Immunization Program recommendation (24⁺⁰/₇ to 36⁺⁶/₇ weeks' gestation) with the receipt of the vaccine 14 days or more before delivery.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lower respiratory Tract Disease (LRTD) Hospitalization among infants aged up to 180 days (Tarsila Inpatient Study)	Hospitalization due to RT-qPCR-confirmed RSV-positive lower respiratory tract disease, defined as cough or difficulty breathing, symptom onset within the preceding 10 days, and at least one of the following: tachypnea (respiratory rate ≥60 breaths/min for infants <2 months; ≥50 breaths/min for infants 2-12 months), oxygen saturation (SpO₂) <95%, or chest wall indrawing).	Hospitalization occurring ≤180 days after birth
Acute respiratory illness (ARI) among infants aged up to 180 days (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive 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).	Occurring ≤180 days after birth.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lower respiratory Tract Disease (LRTD) hospitalization among infants aged up to 180 days by subgroups (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD hospitalization, analyzed by: Gestational age at RSVpreF vaccination.; Time from RSVpreF vaccination to birth.; Time intervals of infant age at illness.	Hospitalization occurring ≤180 days after birth
Severe Lower respiratory Tract Disease (LRTD) hospitalization among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive severe LRTD hospitalization, defined as LRTD plus at least one of the following: respiratory rate ≥70 breaths/min (if <2 months) or ≥60 breaths/min (if ≥2 months); SpO₂ <93%; requirement for high-flow oxygen, non-invasive, or invasive mechanical ventilation; intensive care unit (ICU) admission for >4 hours; or unresponsiveness/loss of consciousness) .	Hospitalization occurring ≤180 days after birth
Severe Lower respiratory Tract Disease (LRTD) hospitalization among infants aged up to 180 days by subgroups (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive severe LRTD hospitalization, analyzed by: Gestational age at RSVpreF vaccination.; Time from RSVpreF vaccination to birth.; Time intervals of infant age at illness.	Hospitalization occurring ≤180 days after birth
Acute respiratory illness (ARI) among infants aged up to 180 days by Subgroups (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive ARI analyzed by: gestational age at RSVpreF vaccination, time from RSVpreF vaccination to birth, and time intervals of infant age at illness.	ARI occurring ≤180 days after birth

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lower respiratory Tract Disease (LRTD) hospitalization among infants aged up to 180 days by exploratory subgroups (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD hospitalization, analyzed by: RSV subtype (RSV-A, RSV-B).; Human milk feeding status (e.g., breastfeeding).; RSVpreF administration with other vaccines received during pregnancy.; RSVpreF vaccination status in a previous pregnancy.	Hospitalization occurring ≤180 days after birth
Lower respiratory Tract Disease (LRTD) ICU hospitalization among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD ICU hospitalization. ICU admission occuring at any point during the index hospitalization.	Hospitalization occurring ≤180 days after birth. ICU admission occuring at any point during the index hospitalization
Lower respiratory Tract Disease (LRTD) prolonged hospitalization among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD long hospital stay (≥11 days) .	Hospitalization occurring ≤180 days after birth
Lower respiratory Tract Disease (LRTD) in-hospital death among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD in-hospital death.	Hospitalization occurring ≤180 days after birth. Death occuring at any point during the index hospitalization.
Hospitalization for lower respiratory tract disease (LRTD) among infants aged up to 360 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive LRTD hospitalization, analyzed by time intervals of infant age at illness.	Hospitalization occurring ≤360 days after birth
Severe lower respiratory Tract Disease (LRTD) hospitalization among infants aged up to 180 days by exploratory subgroups (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive severe LRTD hospitalization analyzed by: RSV subtype (RSV-A, RSV-B).; Human milk feeding status (e.g., breastfeeding).; RSVpreF administration with other vaccines received during pregnancy.; RSVpreF vaccination status in a previous pregnancy.	Hospitalization occurring ≤180 days after birth
Hospitalization for severe lower respiratory tract disease (LRTD) among infants aged up to 360 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive severe LRTD hospitalization analyzed by time intervals of infant age at illness.	Hospitalization occurring ≤360 days after birth
Acute respiratory illness (ARI) hospitalization among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive ARI hospitalization	Hospitalization occurring ≤180 days after birth
Acute respiratory illness (ARI) hospitalization among infants aged up to 360 days (Tarsila Inpatient Study)	RT-qPCR-confirmed RSV-positive ARI hospitalization.	Hospitalization occurring ≤360 days after birth
Lower respiratory Tract Disease (LRTD) Hospitalization due to Human Metapneumovirus (HMPV) among infants aged up to 180 days (Tarsila Inpatient Study)	RT-qPCR-confirmed HMPV-positive LRTD hospitalization	Hospitalization occurring ≤180 days after birth
Acute Respiratory Illness (ARI) among infants aged up to 180 days by exploratory subgroups (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive ARI analyzed by: RSV subtype (RSV-A, RSV-B).; Human milk feeding status (e.g., breastfeeding).; RSVpreF administration with other vaccines received during pregnancy.; RSVpreF vaccination status in a previous pregnancy.	ARI occurring ≤180 days after birth
Acute respiratory illness (ARI) among infants aged up 360 days (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive ARI analyzed by time intervals of infant age at illness.	ARI occurring ≤360 days after birth
Lower respiratory Tract Disease (LRTD) among infants aged up to 180 days (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive LRTD.	LRTD occurring ≤180 days after birth.
Lower respiratory Tract Disease (LRTD) infants aged up to 360 days (Tarsila Outpatient Study)	RT-qPCR-confirmed RSV-positive LRTD.	LRTD occurring ≤360 days after birth.

Collaborators and Investigators

• Sponsor: Inova Medical
• Collaborators: Universidade Federal do Paraná
• Investigators: Principal Investigator: Maicon Falavigna, Inova Medical

Study record dates

Study Major Dates

• Study Start (Estimated): April 30, 2026
• Primary Completion (Estimated): September 30, 2028
• Study Completion (Estimated): December 31, 2028

Study Registration Dates

• First Submitted: February 20, 2026
• First Submitted That Met QC Criteria: February 25, 2026
• First Posted (Actual): March 3, 2026

Study Record Updates

• Last Update Posted (Actual): March 3, 2026
• Last Update Submitted That Met QC Criteria: February 25, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Maternal immunization; respiratory syncytial virus; acute respiratory illness; respiratory syncytial virus bivalent prefusion F vaccine; lower respiratory tract disease; Tarsila study
• Other Study ID Numbers: CAAE 95166426.7.1001.0008

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No