523 documents found, page 1 of 53
Cross-sectional study on protective antibodies against influenza A virus subtyp...
Guiomar, Raquel; Henriques, Camila; Pereira da Silva, Susana; Gomes, Licínia; Dias, Daniela; Verdasca, NunoThe 2025/26 season was marked by co-circulation of influenza A subtypes, with the first detection of A(H3N2) subclade K in September 2025. In August 2025 in Portugal, 14.8% (95% CI: 12.2-17.8) of 886 persons tested had cross-protective antibodies against this subclade. The overall seroprevalence against circulating A(H1N1)pdm09 strains was 28.1% (95% CI: 24.4-32.0). These data highlight the presence of previous...
COVID-19 vaccine effectiveness in the paediatric population aged 5-17 years: a ...
Soares, Patricia; Machado, Ausenda; Nicolay, Nathalie; Monge, Susana; Sacco, Chiara; Hansen, Christian Holm; Meijerink, Hinta; Martínez-Baz, IvánBackground: During the first year of the COVID-19 pandemic, vaccination programmes targeted children and adolescents to prevent severe outcomes of SARS-CoV-2 infection. Aim: To estimate COVID-19 vaccine effectiveness (VE) against hospitalisation due to COVID-19 in the paediatric population, among those with and without previously documented SARS-CoV-2 infection. Methods: We established a fixed cohort followed f...
Surveillance of severe acute respiratory infections associated with SARS-CoV-2,...
Sanchez Ruiz, Miguel Angel; Marques, Diogo Fp.; Lomholt, Frederikke Kristensen; Vestergaard, Lasse Skafte; Monge, Susana; Lozano Álvarez, MarcosBackgrounds: Surveillance of severe acute respiratory infections (SARI) using ICD-10 codes from electronic health records (EHR) lacks consensus on optimal case-defining codes.AIMWe determined codes that maximise sensitivity (Se) and positive predictive value (PPV) for SARI associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus and respiratory syncytial virus (RSV) in Denma...
Recommendations for estimating and reporting vaccine effectiveness by time sinc...
Kissling, Esther; Nunes, Baltazar; Hooiveld, Mariëtte; Martínez-Baz, Iván; Monge, Susana; Robertson, Chris; Knolm, Mirjam; Sève, Noémie; Mlinarić, IvanEstimating COVID-19 vaccine effectiveness (VE) by time since vaccination (TSV) is essential for understanding how protection may change over time and enables meaningful comparisons across studies. This is important for accurate comparisons of VE against different SARS-CoV-2 variants/sublineages, across age groups, during different periods post vaccination campaign, or by vaccine type/brand. We provide recommend...
Long term bivalent mRNA vaccine effectiveness against COVID-19 hospitalisations...
Machado, Ausenda; Kislaya, Irina; Soares, Patricia; Magalhães, Sarah; Nunes, Baltazar; On behalf of PT-EHR vaccine groupBackground: In Autumn 2022, there were recommendations for a COVID-19 booster vaccination with adapted bivalent vaccines to eligible population. Evaluating vaccine effectiveness (VE), in a short period after the vaccination, is key to guide public health decisions on the vaccine performance, allowing implementation of mitigation strategies promptly. However, to assess long-term protection post-vaccination and e...
Effectiveness of JN.1 monovalent COVID-19 vaccination in EU/EEA countries betwe...
Humphreys, James; Blake, Alexandre; Nicolay, Nathalie; Braeye, Toon; Van Evercooren, Izaak; Hansen, Christian Holm; Moustsen-Helms, Ida RaskWe estimated vaccine effectiveness (VE) of Omicron JN.1-adapted COVID-19 vaccines administered during the 2024 autumnal vaccination campaign against COVID-19 hospitalisation and death among eligible individuals aged ≥65 years. The study period was October 2024-January 2025. Using a common protocol across six EU/EEA study sites, we linked electronic health records to construct retrospective cohorts and applied C...
Distribution of the West Nile Virus vector, Culex pipiens, in mainland Portugal...
Martinho, Júlia; Costa Osório, Hugo; Amaro, Fátima; Silva, Manuel; Marques Zé-Zé, Líbia Maria; Pereira Figueira Alves, Maria João; Nunes, BaltazarBackground: Culex pipiens, Portugal’s most abundant mosquito, is a vector for several pathogens including the West Nile virus. Understanding its spatial distribution can contribute to vector-borne diseases control and public health planning, given Portugal’s favourable climate. National-level data on its spatial distribution, especially in relation to climatic variables is limited. We aimed to predict the suita...
The potential bias introduced into COVID-19 vaccine effectiveness studies at pr...
Lanièce Delaunay, Charlotte; Nunes, Baltazar; Monge, Susana; de Lange, Marit; Túri, Gergő; Machado, Ausenda; Latorre-Margalef, Neus; Mlinarić, IvanBackground: With SARS-CoV-2 self-tests, persons with acute respiratory infections (ARI) can know their COVID-19 status. This may alter their decision to consult a general practitioner (GP), potentially biasing COVID-19 vaccine effectiveness (VE) studies. We explore bias mechanisms, simulate magnitude, and verify control methods. Methods: We used directed acyclic graphs (DAGs) to illustrate the bias mechanisms. ...
Evaluation of European severe acute respiratory infection (SARI) surveillance, ...
Marques, Diogo Fp; Kovacs, Dory; Sanchez-Ruiz, Miguel-Angel; Rodrigues, Ana Paula; Machado, Ausenda; Mazagatos, Clara; Monge, Susana; Domegan, LisaBackground: Between 2020 and 2023, ECDC has supported 21 of 30 EU/EEA and six Western Balkan countries by enhancing severe acute respiratory infection (SARI) surveillance to monitor trends, detect unexpected events, evaluate public health interventions, identify risk factors and support vaccine effectiveness studies. Using diverse strategies, countries have implemented SARI surveillance and reported data at nat...
Unmeasured confounding and misclassification in studies estimating vaccine effe...
Humphreys, James; Nicolay, Nathalie; Braeye, Toon; Van Evercooren, Izaak; Holm Hansen, Christian; Moustsen-Helms, Ida Rask; Sacco, ChiaraBackground: Electronic health record (EHR)-based observational studies can rapidly provide real-world data on vaccine effectiveness (VE), though EHR data may be prone to misclassification and unmeasured confounding. Methods: In VEBIS-EHR, a retrospective multi-country COVID-19 VE cohort study, we examined unmeasured confounding using a negative control outcome (death not related to COVID-19) and misclassificati...