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Maternal Immunization With RSVpreF Vaccine: Effectiveness in Preventing Respiratory Syncytial Virus-associated
Angela Gentile1, María Del Valle Juárez1, María Florencia Lucion1
1From the Department of Epidemiology, "Dr Ricardo Gutiérrez" Children's Hospital, Buenos Aires City.
Insights
Maternal immunization with the RSVpreF vaccine significantly reduced hospitalizations in infants under 6 months. Vaccination also decreased the severity of respiratory syncytial virus (RSV) disease in this vulnerable population.
Area of Science:
- Pediatrics
- Immunology
- Public Health
Background:
- Respiratory syncytial virus (RSV) is a major cause of infant illness and death, especially in those younger than six months.
- Argentina initiated a bivalent RSVpreF vaccine program for pregnant women in March 2024 to protect infants during RSV season.
Purpose of the Study:
- To evaluate the effectiveness of maternal RSVpreF immunization in preventing RSV-related hospitalizations in infants under six months.
- To analyze the clinical and epidemiological features of hospitalized infants born to vaccinated and unvaccinated mothers.
Main Methods:
- A multicenter, prospective, observational study utilizing a test-negative design.
- Data collected via active surveillance of respiratory infections in children hospitalized at four pediatric centers in Argentina.
Main Results:
- RSV cases were younger and had fewer comorbidities than RSV-negative controls.
- Maternal RSV immunization was significantly lower in RSV cases (17.6%) compared to controls (44.8%).
- Effectiveness of maternal immunization against RSV hospitalization in infants was 68.2% (crude) and 78.7% (adjusted).
Conclusions:
- The maternal RSVpreF immunization program in Argentina showed significant effectiveness in its first season.
- The vaccine substantially reduced RSV-associated hospitalizations and disease severity in infants under six months.
Background:
Respiratory syncytial virus (RSV) is a leading cause of morbidity and mortality in infants, particularly in those under 6 months. Starting March 2024, Argentina implemented the bivalent RSVpreF vaccine for pregnant women between 32.0 and 36.6 weeks of gestation during the RSV season. This report study aimed to assess the effectiveness of maternal immunization in preventing RSV-associated hospitalizations in infants under 6 months born to vaccinated and not vaccinated women, including their clinical and epidemiological characteristics.
Methods:
A multicenter, prospective, observational, nested case-control study using a test-negative design was conducted. Data were collected through active epidemiological surveillance of respiratory infections in children under 18 years of age hospitalized at 4 pediatric referral hospitals in Argentina.
Results:
Between January and October 2024, 1340 children were hospitalized for respiratory infections, including 187 infants born after March 15: 91 RSV-positive cases and 96 RSV-negative controls. RSV cases peaked in epidemiological week 26 (June). Compared to controls, RSV cases were younger ( P < 0.001) and had lower frequencies of comorbidities ( P < 0.001), prematurity ( P = 0.016) and chronic respiratory diseases ( P < 0.001). RSV maternal immunization was less frequent among RSV cases than controls (17.6% vs. 44.8%; P < 0.001). Vaccinated RSV cases had shorter duration of oxygen therapy (4 vs. 7 days; P < 0.001) and hospital stay (5 vs. 8 days; P < 0.001). The crude effectiveness of RSV immunization in infants under 6 months was 68.2% (95% confidence interval: 33.1%-84.9%) and 78.7% (95% confidence interval: 51.4%-90.7%) after adjustment for age under 3 months, prematurity and chronic respiratory disease.
Conclusion:
In its first season, Argentina's maternal RSVpreF immunization demonstrated substantial effectiveness in reducing RSV-associated hospitalizations in infants and decreasing RSV disease severity.
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