Percorrer por autor "Saraiva, Ana Leonor"
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- Actividade Dinâmica para a Noite Europeia dos Investigadores 2025Publication . Brito, André; Saraiva, Ana LeonorDashboard interactivo desenhando especificamente para apresentar o trabalho do DEP na Noite Europeia dos Investigadores em 2025 em Lisboa. Inclui duas actividades, uma que apresenta de forma dinâmica como é feita a modelação matemática de dinâmicas de doença com modelos compartimentais com exemplos e histórias ilustrativas e uma outra atividade que apresenta como são estimados o risco de morte em caso de exposição a temperaturas altas.
- Development and Application of a Harmonization Method for IgG Antibody Levels Against SARS-CoV-2S pike Protein: A Cohort Study in Healthcare ProfessionalsPublication . Saraiva, Ana Leonor; Afreixo, Vera; Gaio, Vânia; Machado, AusendaIntroduction: The emergence of COVID-19 led to the rapid development of vaccines and diagnostic tests. To assess antibody responses in healthcare workers (HCWs), a 2021–2022 cohort study was conducted in three Portuguese hospitals. Antibody levels were measured at six time points: pre-vaccination, post-first dose, at 3, 6, 12 months after the second dose, and post-booster. Each hospital utilized a different assay: Abbott’s CMIA, Roche’s Elecsys® ECLIA, and Siemens’ ADVIA Centaur®, leading to challenges in data comparability. The study aimed to harmonize serological data across these hospitals to enable joint analysis and better understand the dynamics of humoral immunity among HCWs in Portugal. Methods: To ensure adequate conversion of antibody titers obtained from different laboratory methods, several harmonization strategies were applied and compared. These included the World Health Organization (WHO) international conversion and a main strategy based on quantile interpolation, with linear and spline methods tested, followed by Deming regression. Before interpolation, models were required to estimate the antibody titers due to the limitations of each method, such as linear regressions with polynomials and splines, followed by data linearization and normalization. The final choice between methods was based on a graphical assessment of which approach best preserved the original data patterns prior to harmonization. Results: The application of quantile interpolation followed by regression proved more effective than the WHO recommended approach for harmonizing data across hospitals. This method preserved the individual distribution patterns of each hospital, even after transformation. Importantly, it allowed the harmonized values to reflect the scale and magnitude observed in the reference method (Abbott’s CMIA). After harmonization, a marked increase was observed between the pre-vaccination time point and the post-vaccination time point, followed by a gradual decrease over the next three time points. Finally, a second, even more pronounced increase was observed after the booster dose. Conclusions: Quantile interpolation followed by regression enabled effective harmonization of serological data across the hospital centers, allowing for the comparison and joint analysis of anti-SARS-CoV-2 IgG antibody titers from different laboratory methods. This approach also preserved the expected temporal antibody response pattern. Although laboratory validation, by quantifying the same samples across different laboratories, was not performed, which would be necessary to fully confirm the adequacy of the method, the presented methodology shows strong applicability to other contexts, particularly in European studies that conduct pooled analyses of data from multiple countries and laboratories.
- Linear Regression Analysis of Harmonized IgG Antibody Levels Against the SARS-CoV-2 Spike Protein: A Cohort Study in Healthcare WorkersPublication . Saraiva, Ana Leonor; Afreixo, Vera; Machado, Ausenda; Gaio, VâniaThe emergence of COVID-19 in 2019 led to the rapid development of vaccines and diagnostic tests. To assess antibody responses in healthcare workers (HCWs), a cohort study was conducted between 2021 and 2022 across three Portuguese hospitals. Antibody levels were measured at six time points: prevaccination, post-vaccination, and at 3, 6, and 12 months after the vaccination, as well as after the booster dose. Each hospital used a different assay: Abbott’s CMIA, Roche’s Elecsys® ECLIA, and Siemens’ ADVIA Centaur®, posing challenges for data comparability. The study aimed to harmonize serological data across these hospitals and to model antibody increases and decreases over time using linear regression. To ensure adequate conversion of antibody titers from different laboratory methods, quantile harmonization, and Deming regression were applied. After harmonization, three linear regressions were fitted: one for the increase between prevaccination and post-vaccination, another for the decrease between post-accination and 12 months after vaccination, and finally, one for the increase between 12 months after vaccination and after the booster dose. Models included variables such as prior infection, age, hospital, smoking status, contact with COVID-19 patients, and chronic conditions. In the phase-specific analysis, in addition to variations between hospitals in the regression of the last increase after the booster dose, it was observed that individuals over 50 years of age exhibited a superior immune response (811 550; IC 95%: 598 774, 1 024 327; p < 0.001). This higher percentage increase may be explained by initially lower levels, unlike younger individuals who had higher titers.
- Longitudinal dynamics of humoral immunity among health care workers in Portugal using mixed effects modellingPublication . Saraiva, Ana Leonor; Afreixo, Vera; Machado, Ausenda; Gaio, VâniaIntroduction: The emergence of COVID-19 in 2019 led to the rapid development of vaccines and diagnostic tests. To assess antibody responses in healthcare workers (HCWs), a 2021–2022 cohort study was conducted across three Portuguese hospitals. Antibody levels were measured at six intervals: pre-vaccination, post-first dose, at 3, 6, and 12 months after the second dose, and post-booster. Each hospital utilized a different assay: Abbott’s CMIA,, Roche’s Elecsys® ECLIA, and Siemens’ ADVIA Centaur®, leading to challenges in data comparability. The study aimed to harmonize serological data across these hospitals and, through mixed-effects modeling, jointly analyze the longitudinal dynamics of humoral immunity among HCWs in Portugal. Methods: To ensure adequate conversion of antibody titers from different laboratory methods, quantile harmonization, and Deming regression were applied. After harmonization, linear mixed-effects models (LMER) assessed the relationship between antibody levels and covariates, accounting for fixed and random effects. The models included variables such as prior infection, age, hospital, smoking status, contact with COVID-19 patients, and chronic conditions. Sensitivity analyses included models excluding outliers, removing influential points, and applying multiple imputation for missing data. Results: The mixed-effects models demonstrated significant increases in antibody levels following vaccination (β = 21,234; 95% CI: 14,014–28,454; p < 0.001), with an even greater rise observed after the booster dose (β = 33,185; 95% CI: 25,939–40,430; p < 0.001) when compared to the pre-vaccination baseline. Significant differences between hospitals were also evident, as Roche’s Elecsys® ECLIA showed a notably smaller increase at 3 months compared to Abbott’s CMIA (β = -3,285; 95% CI: -5,511 to -1,058; p = 0.004). Interaction plots highlighted how covariates influenced antibody levels over time, revealing higher antibody responses post-vaccination and booster among individuals with prior infection, younger age groups, non-smokers, healthcare workers with direct patient contact, and those without chronic conditions. Sensitivity analyses, such as removing outliers and influential points and applying multiple imputation for missing data, confirmed the robustness and reliability of these findings. Conclusions: The harmonization of antibody measurements enabled a clear evaluation of immune response dynamics among healthcare workers. Vaccination and booster doses significantly increased antibody levels, while differences between hospitals and individual characteristics influenced the magnitude of these responses. These findings enhance our understanding of factors shaping humoral immunity and may guide future vaccination strategies.
- Psychosocial factors of vaccine confidence: an exploratory study among Portuguese healthcare workersPublication . Gaio, Vânia; Saraiva, Ana Leonor; Santos, Ana João; Amaral, Palmira; Machado, AusendaBackground: Healthcare workers (HCWs) play a critical role in vaccination uptake, both through personal adherence and by promoting immunisation among patients. Low vaccine confidence among HCWs can undermine public health efforts by reducing personal vaccination rates, but also impacting vaccine recommendations. This study aimed to assess psychosocial determinants influencing vaccine confidence among HCWs in Portugal. Methods: A cross-sectional study was conducted between October and November 2024 among doctors and nurses from a Portuguese healthcare unit. An online questionnaire incorporating an adapted short version of the Professionals Vaccine Confidence and Behaviors (Pro-VC-Be) scale was applied. Exploratory factor analysis (EFA) was conducted to assess the scale’s unidimensionality. Descriptive statistics, bivariate analyses (vaccinated vs. non-vaccinated) using Fisher’s exact and Pearson’s Chi-squared tests were performed to identify key psychosocial dimensions of vaccine confidence. Results: Among 112 HCWs (82% female; 71% nurses), 67% were vaccinated against COVID-19 in the 2024/25 season. EFA suggested an unidimensional structure, with one dominant factor (eigenvalue=1.90) explaining 56% of the variance. Vaccinated HCWs showed significantly higher confidence scores (mean=42.9 vs. 40.8; p=0.003). Trust in vaccine safety (p=0.027), belief in vaccine benefits (p=0.011), and complacency (p=0.048) were positively associated with COVID-19 vaccination status. Conclusions: This exploratory study highlights key psychosocial determinants of vaccine confidence among Portuguese HCWs, notably perceived safety and effectiveness. Given the small sample size, results should be interpreted with caution. Applying the scale to a larger and more diverse population of HCWs is essential to validate these findings and support the development of targeted strategies focusing on building trust and combating misinformation to enhance vaccine uptake.