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. 2025 Apr;30(14):2400637.
doi: 10.2807/1560-7917.ES.2025.30.14.2400637.

Impact of routine prophylaxis with monoclonal antibodies and maternal immunisation to prevent respiratory syncytial virus hospitalisations, Lombardy region, Italy, 2024/25 season

Francesco Menegale  1   2 , Luigi Vezzosi  3 , Marcello Tirani  3 , Simona Scarioni  3 , Stefano Odelli  3 , Federica Morani  3 , Catia Borriello  3 , Elena Pariani  4 , Ilaria Dorigatti  5 , Danilo Cereda  3 , Stefano Merler  2 , Piero Poletti  2
Affiliations

Impact of routine prophylaxis with monoclonal antibodies and maternal immunisation to prevent respiratory syncytial virus hospitalisations, Lombardy region, Italy, 2024/25 season

Francesco Menegale et al. Euro Surveill. 2025 Apr.

Abstract

BackgroundRespiratory syncytial virus (RSV) is a leading cause of hospitalisation in children worldwide. Recent regulatory approval of monoclonal antibody (mAb) nirsevimab for infants and the RSVpreF vaccine for pregnant women offers promising approaches to mitigate RSV-associated morbidity.AimTo evaluate potential impacts of routine prophylactic campaigns (mAbs targeting infants or maternal vaccination) introduced in the 2024/25 season on hospitalisations from RSV lower respiratory tract infections in Lombardy, Italy.MethodsWe used a catalytic model informed by data from pre-COVID-19 pandemic (before 2020) and post-pandemic periods (until 2022) to quantify the number of cases and hospitalisations that could be averted by seasonal nirsevimab administration to infants and RSVpreF maternal vaccination, considering changes in susceptibility caused by reduced RSV circulation during the pandemic.ResultsAs a marked proportion of RSV hospitalisations occurs in infants aged ≤ 1 year, seasonal mAb administration to 80% of newborns (uptake levels observed in Spain) was estimated to avert 50.2% (95% CI: 43.5-55.8) of hospitalisations in the total population. Coverage levels close to those observed for childhood vaccines (95%) could result in an additional average 18% reduction in hospitalisations. Vaccination of 65% of pregnant women, resembling the diphtheria-tetanus-pertussis vaccine coverage in Lombardy for this population, was estimated to avert 30.5% (95% CI: 19.6-39.7) of hospitalisations. At influenza vaccine coverage (12%), less than 8% of hospitalisations could be averted by maternal immunisation.ConclusionRoutine nirsevimab administration to infants demonstrates clear potential to reduce RSV-associated hospitalisations. Maternal immunisation can help in achieving high protection in at-risk populations.

Keywords: immunization programs; maternally-acquired immunity; monoclonal antibodies; respiratory syncytial virus; respiratory syncytial virus vaccines; transmission model.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Model estimates of RSV susceptibility over time under the baseline scenario (no interventions), Lombardy, Italy, 2018/19–2024/25 seasons
Figure 2
Figure 2
Impact of different immunisation strategies on the age-stratified incidence of RSV-attributable cases and hospitalisations, Lombardy, Italy, 2024/25 season
Figure 3
Figure 3
Expected proportion of RSV hospitalisations averted in the overall population by different immunisation strategies for varying coverage levels, Lombardy, Italy, 2024/25 season
See this image and copyright information in PMC

References

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