Impact of national RSV immunization programme on the epidemiology of bronchiolitis in Greece
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Updated: Oct 31, 2026

An Improved and High Throughput Respiratory Syncytial Virus (RSV) Micro-neutralization Assay
Published on: January 26, 2019
Argyro Konstantopoulou1,2, Kyriaki Velali1, Panagiota Markopoulou1,3
1First Department of Pediatrics, Medical School, National and Kapodistrian University of Athens, Athens, Greece.
Abstract:
Universal RSV immunization strategies for infants, including monoclonal antibody administration and maternal vaccination during pregnancy, were implemented in Greece for the first time during the 2025-2026 season. We conducted a prospective observational study of infants aged <12 months hospitalized with bronchiolitis at a quaternary paediatric hospital in Greece between November 2025 and April 2026. Bronchiolitis incidence was compared with that of the 2023-2024 and 2024-2025 seasons. Severity of bronchiolitis was assessed using the modified Tal score. Across the three seasons, 854 of 15246 admissions were due to bronchiolitis. The incidence decreased significantly in 2025-2026 to 42 per 1000 admissions, compared to 64 and 59 in 2024-2025 and 2023-2024, respectively. The 2025-2026 epidemic curve of bronchiolitis was flatter and more prolonged, with a delayed peak in March. Of 186 infants with bronchiolitis, 19.9% had received RSV immunization. Disease severity and oxygen requirements did not differ significantly between immunized and unimmunized infants, although unimmunized infants were older and had a trend towards higher complication rates. In conclusion, national RSV immunization was associated with reduced bronchiolitis hospitalizations and complications. However, the smaller-than-expected reduction in disease rates underscores the need to improve awareness, coverage, and timely immunization.
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