Effectiveness of Immunization in Preventing Severe Acute Respiratory Infection RSV

December 1, 2025 updated by: Bogotá District Health Secretariat

Effectiveness of Immunization in Preventing Severe Acute Respiratory Infection Associated With Respiratory Syncytial Virus-RSV- in Infants Under 6 Months of Age in Bogotá: a Case-control Study With a Negative Test Design

This study aims to evaluate the real-world effectiveness of two preventive immunization strategies against Respiratory Syncytial Virus (RSV)-associated severe acute respiratory infection in infants less than six months of age in Bogotá, Colombia. The strategies include maternal vaccination with RSVpreF administered between 28 and 36 weeks of gestation and neonatal immunization with nirsevimab for infants born to mothers who did not receive RSVpreF during pregnancy. Using a test-negative case-control design embedded in the city's sentinel surveillance system, infants hospitalized for severe respiratory infection will be systematically tested for RSV. Comparative vaccine effectiveness will be estimated to determine the impact of maternal RSV vaccination and neonatal monoclonal antibody immunization on RSV-associated hospitalizations, intensive care admissions, and mortality. The study will generate real-world evidence to inform local and regional public health decisions and guide the implementation of cost-effective hybrid immunization strategies against RSV in middle-income settings.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Respiratory Syncytial Virus (RSV) is a leading cause of hospitalization, morbidity, and mortality among infants, particularly during the first months of life. In 2026, Bogotá will introduce a hybrid immunization strategy combining maternal vaccination with RSVpreF during weeks 28-36 of pregnancy and neonatal immunization with nirsevimab for infants whose mothers were not vaccinated. Despite evidence from clinical trials, real-world comparative effectiveness data for hybrid RSV immunization strategies in Latin America remain limited.

This observational study will employ a prospective test-negative case-control design using the city's sentinel surveillance network for severe respiratory infection. All eligible infants under six months hospitalized for severe acute respiratory infection will undergo laboratory testing for RSV. Cases will be defined as RSV-positive infants, and controls as RSV-negative infants. Exposure to RSVpreF or nirsevimab will be validated through Bogotá's immunization registry.

Primary outcomes include laboratory-confirmed RSV-associated hospitalization, admission to intensive care, and death within the first six months of life. Multilevel logistic regression models adjusted for relevant confounders will be used to estimate vaccine effectiveness. Findings will provide rigorous real-world evidence to support policy decisions, optimize resource allocation, and guide the expansion of hybrid RSV prevention strategies in Colombia and other middle-income countries.

Study Type

Observational

Enrollment (Estimated)

1097

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Infants younger than six months residing in Bogotá, Colombia, hospitalized for severe acute respiratory infection in sentinel hospitals and tested for RSV within 48 hours of admission. The population includes infants exposed to maternal RSVpreF vaccination, neonatal nirsevimab, or neither intervention. Extremely preterm infants (≤32 weeks gestation) and those hospitalized for non-respiratory conditions are excluded.

Description

Inclusion Criteria:

  • Age: Infants younger than 6 months at the time of hospital admission.
  • Residence: Maternal residence in Bogotá, Colombia, verified through clinical record, identification document, or health system registry.
  • Clinical Condition: Hospitalization due to severe acute respiratory infection (SARI) meeting the district operational definition (presence of fever, cough, and/or signs of respiratory distress, requiring inpatient management).
  • Laboratory Testing: Respiratory specimen collected and tested for RSV by RT-PCR or validated antigen test within ≤48 hours of hospital admission, or repeated within 24-48 hours if initial test is negative.
  • Exposure Eligibility Window: Infant born ≥5 weeks after the start of the RSVpreF maternal vaccination campaign in Bogotá, ensuring opportunity for maternal immunization.

Exclusion Criteria:

  • Prematurity: Infants born at ≤32 weeks of gestation.
  • Healthcare-associated respiratory infection: Symptom onset >48 hours after hospital admission for another condition.
  • Non-respiratory hospital admission: Primary reason for hospitalization unrelated to respiratory disease (e.g., trauma, elective surgery).
  • Vaccination status unverifiable: Inability to confirm maternal RSVpreF vaccination status after reasonable attempts to verify through registry, vaccination card, or prenatal documentation.
  • Duplicate episodes: Readmission for the same respiratory episode ≤14 days after discharge (only the first episode will be included).
  • Delayed sampling: First respiratory sample obtained >48-72 hours after initial admission to the health system.
  • Lethal congenital conditions: Congenital or genetic disorders incompatible with life or that substantially alter the expected clinical course.
  • Concurrent interventional study participation: Enrollment in another clinical trial that may affect respiratory outcomes.
  • Inability to establish mother-infant linkage due to adoption, loss of parental custody, or absence of biological maternal records.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Case (RSV-positive test result)
An infant younger than six months of age, resident in Bogotá, hospitalized for severe acute respiratory infection (SARI) and meeting the district operational criteria for SARI, who has a respiratory specimen collected within ≤48 hours of hospital admission (or repeated within 24-48 hours if the first result was negative) that tests positive for Respiratory Syncytial Virus (RSV) by RT-PCR or a validated antigen assay. Only infants born ≥5 weeks after the start of the maternal RSVpreF vaccination campaign are eligible for inclusion.
Biological: RSVpreF vaccine (Abrysvo) and Nirsevimab (Beyfortus) or unexposed
Maternal vaccination administered between 28 and 36 weeks of gestation and Single-dose monoclonal antibody administered to newborns whose mothers did not receive effective RSVpreF vaccination or unexposed
Control (RSV-negative test result)
An infant younger than six months of age, resident in Bogotá, hospitalized for severe acute respiratory infection (SARI) and meeting the same operational criteria as cases, who has a respiratory specimen collected within ≤48 hours of admission (or repeated within 24-48 hours if needed) that tests negative for RSV. Controls may test positive for other respiratory viruses or bacteria. Only infants born ≥5 weeks after the start of the maternal RSVpreF vaccination campaign are eligible.
Biological: RSVpreF vaccine (Abrysvo) and Nirsevimab (Beyfortus) or unexposed
Maternal vaccination administered between 28 and 36 weeks of gestation and Single-dose monoclonal antibody administered to newborns whose mothers did not receive effective RSVpreF vaccination or unexposed

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Hospitalization for RSV-associated Severe Acute Respiratory Infection
Time Frame: From birth up to 6 months of age (≤180 days of life)
Proportion of infants hospitalized with laboratory-confirmed Respiratory Syncytial Virus (RSV)-associated severe acute respiratory infection, defined as meeting the district operational criteria for SARI and testing positive for RSV by RT-PCR or validated antigen testing within ≤48 hours of hospital admission. The measure compares the likelihood of RSV-related hospitalization among infants exposed to maternal RSVpreF vaccination, neonatal nirsevimab administration, or no RSV-specific immunization.
From birth up to 6 months of age (≤180 days of life)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Bogotá District Health Secretariat

Investigators

  • Principal Investigator: Julián Alfredo Fernández Niño, Bogotá District Health Secretariat

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 1, 2026

Primary Completion (Estimated)

December 31, 2026

Study Completion (Estimated)

July 31, 2027

Study Registration Dates

First Submitted

December 1, 2025

First Submitted That Met QC Criteria

December 1, 2025

First Posted (Actual)

December 12, 2025

Study Record Updates

Last Update Posted (Actual)

December 12, 2025

Last Update Submitted That Met QC Criteria

December 1, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • SDSCTI20250014

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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Clinical Trials on RSVpreF vaccine (Abrysvo) and Nirsevimab (Beyfortus) or unexposed

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