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Nirsevimab has been recently licensed for universal RSV prophylaxis in infants. NIRSE-GAL is a three-year population-based study initiated in Galicia in September 2023. It aims to evaluate nirsevimab effectiveness against RSV-related hospitalizations lower respiratory tract infections (LRTI), severe RSV, all-cause LRTI, and all-cause hospitalization. NIRSE-GAL also aims to estimate nirsevimab impact on primary healthcare use in the short and mid-term, children's wheezing and asthma, and medical prescriptions for RSV. The immunization campaigns will be scheduled based on the expected start week for the RSV season and will last the whole season. Immunization will be offered to: i) infants born during the campaign (seasonal), ii) infants < 6 months at the start of the campaign (catch-up), and iii) infants with high-risk factors, aged 6-24 months at the start of the campaign (high-risk). The follow-up period will start: i) the immunization date for all immunized infants, ii) the start of the campaign, for the non-immunized catch-up or high-risk groups, or iii) the birthdate for the non-immunized seasonal group. Infants will be followed up until outcome occurrence, death, or end of study. Nirsevimab effectiveness will be estimated using Poisson and Cox regression models. Sensitivity and stratified analyses will be undertaken. The number of averted cases and the number needed to immunize will be estimated. Immunization failure and nirsevimab safety will be monitored. NIRSE-GAL was approved by the ethics committee of Galicia (CEIC 2023-377) and registered in ClinicalTrials.gov (ID: NCT06180993). Findings will be mainly shared via peer-reviewed publications and scientific conferences.

Background: Galicia (Spain) was one of the first regions worldwide to incorporate nirsevimab for universal respiratory syncytial virus (RSV) prophylaxis in infants into its immunisation programme. The NIRSE-GAL longitudinal population-based study aimed to assess nirsevimab effectiveness in preventing hospitalisations (ie, admittance to hospital)., Methods: The 2023-24 immunisation campaign with nirsevimab in Galicia began on Sept 25, 2023, and concluded on March 31, 2024. The campaign targeted three groups: infants born during the campaign (seasonal group), infants younger than 6 months at the start of the campaign (catch-up group), and infants aged 6-24 months with high-risk factors at the start of the campaign (high-risk group). Infants in the seasonal group were offered immunisation on the first day of life before discharge from hospital. Infants in the catch-up and high-risk groups received electronic appointments to attend a public hospital or health-care centre for nirsevimab administration. For this interim analysis, we used data collected from Sept 25 to Dec 31, 2023, from children born up to Dec 15, 2023. Data were retrieved from public health registries. Nirsevimab effectiveness in preventing RSV-associated lower respiratory tract infection (LRTI) hospitalisations; severe RSV-related LRTI requiring intensive care unit admission, mechanical ventilation, or oxygen support; all-cause LRTI hospitalisations; and all-cause hospitalisations was estimated using adjusted Poisson regression models. Data from five past RSV seasons (2016-17, 2017-18, 2018-19, 2019-20, and 2022-23), excluding the COVID-19 pandemic period, were used to estimate the number of RSV-related LRTI hospitalisations averted along with its IQR. The number needed to immunise to avoid one case in the 2023-24 season was then estimated from the averted cases. Nirsevimab safety was routinely monitored. The NIRSE-GAL study protocol was registered on ClinicalTrials.gov (NCT06180993), and follow-up of participants is ongoing., Findings: 9408 (91·7%) of 10 259 eligible infants in the seasonal and catch-up groups received nirsevimab, including 6220 (89·9%) of 6919 in the catch-up group and 3188 (95·4%) of 3340 in the seasonal group. 360 in the high-risk group were offered nirsevimab, 348 (97%) of whom received it. Only infants in the seasonal and catch-up groups were included in analyses to estimate nirsevimab effectiveness and impact because there were too few events in the high-risk group. In the catch-up and seasonal groups combined, 30 (0·3%) of 9408 infants who received nirsevimab and 16 (1·9%) of 851 who did not receive nirsevimab were hospitalised for RSV-related LRTI, corresponding to an effectiveness of 82·0% (95% CI 65·6-90·2). Effectiveness was 86·9% (69·1-94·2) against severe RSV-related LRTI requiring oxygen support, 69·2% (55·9-78·0) against all-cause LRTI hospitalisations, and 66·2% (56·0-73·7) against all-cause hospitalisations. Nirsevimab effectiveness against other endpoints of severe RSV-related LRTI could not be estimated because of too few events. RSV-related LRTI hospitalisations were reduced by 89·8% (IQR 87·5-90·3), and the number needed to immunise to avoid one RSV-related LRTI hospitalisation was 25 (IQR 24-32). No severe adverse events related to nirsevimab were registered., Interpretation: Nirsevimab substantially reduced infant hospitalisations for RSV-associated LRTI, severe RSV-associated LRTI requiring oxygen, and all-cause LRTI when given in real-world conditions. These findings offer policy makers and health authorities robust, real-world, population-based evidence to guide the development of strategies for RSV prevention., Funding: Sanofi and AstraZeneca., Translation: For the Spanish translation of the abstract see Supplementary Materials section., Competing Interests: Declaration of interests FM-T reports having acted as principal investigator in randomised controlled trials for Ablynx, Abbott, Seqirus, Sanofi Pasteur, Cubist, Wyeth, Merck, Pfizer, Roche, Regeneron, Jansen, Medimmune, Novavax, Novartis, and GSK, with honoraria paid to his institution and relationships with GSK Vaccines, Pfizer, Sanofi Pasteur, Janssen Pharmaceuticals, MSD, and Seqirus that include consulting or advisory roles. RK, JJ, and LP-A are Sanofi employees and hold shares or stock options in the company. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Objective: In Galicia, the incidence (I) of hepatitis A (HA) is low and the susceptibility is 51% in adults (18-64 years). Between 2016 and 2018 the cases increased, mainly in men. We intend to describe the cases of HA in Galicia during this outbreak period (PB), compare them with the pre-outbreak period (PPB), and the interventions performed., Methods: Descriptive study of the cases of HA declared between 2016-18 (PB), compared to those from the previous period (2010-2015, PPB). Cases recorded in the mandatory notification system (general practice, hospitalization and microbiology) from 2010 to 2018 were included. For the pre-outbreak period 2010-2015 (PPB) it was calculated the average of cases/four-week period to compare observed/expected cases; the incidence (I) [cases/100,000 inhabitants (c/105h)] by sex and age was compared with the PPB through the Relative Risk (RR). It were sent messages with recommendations through men who have sex with men (MSM) reference websites., Results: The outbreak lasted 80 weeks (september of 2016 to march of 2018). The incidence was 3 cases/105h in men and 0.5 cases/105h in women. Compared to the PPB, the RR-PB in men was 4.8 (95%CI=4-7) and 20.4 (95%CI=5-87) in 40-44 years. 42% of men declared to have relationships with other men (57% in 20-30 years). At the end of 2016, a message with recommendations (specially vaccination) was sent via Wapo (promoted to MSM through one of its reference websites), where 331 entries were registered., Conclusions: HA's incidence, in Galicia, increased in 2016-2018 by an outbreak in MSM. We found an increased susceptibility among young people which makes necessary to insist on the vaccination of groups at risk., Competing Interests: Disclosure María Jesús Purriños-Hermida has a temporal consulting agreement with Shionogi SL, for the realization of a decalogue on the importance of antimicrobial resistance. The rest of the authors report no conflicts of interest in this work.