Effectiveness of nirsevimab immunoprophylaxis against respiratory syncytial virus-related outcomes in hospital and primary care settings: a retrospective cohort study in infants in Catalonia (Spain).

BACKGROUND: In Catalonia, infants under 6 months old were eligible to receive nirsevimab, a novel monoclonal antibody against respiratory syncytial virus (RSV). We aimed to analyse nirsevimab's effectiveness across primary and hospital care outcomes. METHODS: Retrospective cohort study from 1 October 2023 to 31 January 2024, including all infants born between April and September 2023. We established two cohorts based on nirsevimab administration (immunised and non-immunised). We followed individuals until the earliest moment of an outcome-RSV infection, primary care attended bronchiolitis and pneumonia, hospital emergency visits due to bronchiolitis, hospital admission or intensive care unit (ICU) admission due to RSV bronchiolitis-death or the end of the study. We used the Kaplan-Meier estimator and fitted Cox regression models using a calendar time scale to estimate HRs and their 95% CIs. RESULTS: Among 26 525 infants, a dose of nirsevimab led to an adjusted HR for hospital admission due to RSV bronchiolitis of 0.124 (95% CI: 0.086 to 0.179) and an adjusted HR for ICU admission of 0.099 (95% CI: 0.041 to 0.237). Additionally, the adjusted HRs observed for emergency visits were 0.446 (95% CI: 0.385 to 0.516) and 0.393 (95% CI: 0.203 to 0.758) for viral pneumonia, 0.519 (95% CI: 0.467 to 0.576) for bronchiolitis attended in primary care and 0.311 (95% CI: 0.200 to 0.483) for RSV infection. CONCLUSION: We demonstrated nirsevimab's effectiveness with reductions of 87.6% and 90.1% in hospital and ICU admissions, respectively. These findings offer crucial guidance for public health authorities in implementing RSV immunisation campaigns.

Measles, mumps, and rubella vaccination coverage: an ecological study of primary health care and socio-economic factors in Catalonia, Spain.

This study examined the association of socio-economic factors and the structure of primary care centres (PCCs) with measles, mumps, and rubella (MMR) vaccination coverage among the 8-year-old population in Catalonia, Spain. We conducted an ecological study to retrospectively assess the MMR vaccination-recorded status of children born in 2012, using public health data extracted in December 2020. For each of 300 PCCs serving 70,498 children, we calculated vaccination coverage rates from electronic health records and linked these rates to a composite deprivation index corresponding to the territory served by each PCC. We identified a relationship between unfavourable socio-economic factors and higher recorded vaccination coverage. On average, directly managed PCCs had higher vaccination coverage rates than indirectly managed PCCs. Greater utilisation of primary care services by the population was also associated with higher vaccination coverage rates. Further research is needed to generate knowledge valuable for informing more equitable child-vaccination service delivery models.