Effectiveness of influenza vaccination in preventing influenza in primary care, Navarre, Spain, 2021/22.

Compared with individuals unvaccinated in the current and three previous influenza seasons, in 2021/22, influenza vaccine effectiveness at primary care level was 37% (95% CI: 16 to 52) for current season vaccination, regardless of previous doses, and 35% (95% CI: -3 to 45) for only previous seasons vaccination. Against influenza A(H3N2), estimates were 39% (95% CI: 16 to 55) and 24% (95% CI: -8 to 47) suggesting moderate effectiveness of current season vaccination and possible remaining effect of prior vaccinations.

Independent Role of Severe Obesity as a Risk Factor for COVID-19 Hospitalization: A Spanish Population-Based Cohort Study.

OBJECTIVES: This study analyzed the association between severe obesity and coronavirus disease 2019 (COVID-19) hospitalization and severe disease. METHODS: The incidence of hospitalization for laboratory-confirmed COVID-19 was evaluated in a prospective population-based cohort of 433,995 persons aged 25 to 79 years in Spain during March and April of 2020. Persons with and without class 3 obesity were compared using Poisson regression to estimate the adjusted relative risk (aRR) from class 3 obesity of COVID-19 hospitalization and of severe disease (intensive care unit admission or death). Differences in the effect by age, sex, and chronic conditions were evaluated. RESULTS: Individuals with class 3 obesity had a higher risk of hospitalization (aRR = 2.20, 95% CI: 1.66-2.93) and developing severe COVID-19 (aRR = 2.30, 95% CI: 1.20-4.40). In people younger than 50 years, these effects were more pronounced (aRR = 5.02, 95% CI: 3.19-7.90 and aRR = 13.80, 95% CI: 3.11-61.17, respectively), whereas no significant effects were observed in those aged 65 to 79 years (aRR = 1.22, 95% CI: 0.70-2.12 and aRR = 1.42, 95% CI: 0.52-3.88, respectively). Sex and chronic conditions did not modify the effect of class 3 obesity in any of the outcomes. CONCLUSIONS: Severe obesity is a relevant risk factor for COVID-19 hospitalization and severity in young adults, having a magnitude similar to that of aging. Tackling the current obesity pandemic could alleviate the impact of chronic and infectious diseases.

Household transmission of influenza A(H1N1)pdm09 in the pandemic and post-pandemic seasons.

BACKGROUND: The transmission of influenza viruses occurs person to person and is facilitated by contacts within enclosed environments such as households. The aim of this study was to evaluate secondary attack rates and factors associated with household transmission of laboratory-confirmed influenza A(H1N1)pdm09 in the pandemic and post-pandemic seasons. METHODS: During the 2009-2010 and 2010-2011 influenza seasons, 76 sentinel physicians in Navarra, Spain, took nasopharyngeal and pharyngeal swabs from patients diagnosed with influenza-like illness. A trained nurse telephoned households of those patients who were laboratory-confirmed for influenza A(H1N1)pdm09 to ask about the symptoms, risk factors and vaccination status of each household member. RESULTS: In the 405 households with a patient laboratory-confirmed for influenza A(H1N1)pdm09, 977 susceptible contacts were identified; 16% of them (95% CI 14-19%) presented influenza-like illness and were considered as secondary cases. The secondary attack rate was 14% in 2009-2010 and 19% in the 2010-2011 season (p=0.049), an increase that mainly affected persons with major chronic conditions. In the multivariate logistic regression analysis, the risk of being a secondary case was higher in the 2010-2011 season than in the 2009-2010 season (adjusted odds ratio: 1.72; 95% CI 1.17-2.54), and in children under 5 years, with a decreasing risk in older contacts. Influenza vaccination was associated with lesser incidence of influenza-like illness near to statistical significance (adjusted odds ratio: 0.29; 95% CI 0.08-1.03). CONCLUSION: The secondary attack rate in households was higher in the second season than in the first pandemic season. Children had a greater risk of infection. Preventive measures should be maintained in the second pandemic season, especially in high-risk persons.

Influencia del criterio de selección de pacientes para la toma de frotis en la estimación de la efectividad de la vacuna antigripal / Influence of distinct criteria for selecting patients for swabbing on estimation of the effectiveness of the influenza vaccine

Objetivo: estimar la efectividad de la vacuna antigripal según el criterio de selección en la toma de frotis. Método: estudio de casos y controles de casos confirmados (n = 909) y controles negativos para gripe (n = 732) en las temporadas 2010-2011 a 2012-2013 en Navarra. La efectividad ajustada de la vacuna se estimó incluyendo todos los frotis de pacientes con síndrome gripal y seleccionando sólo los dos primeros por médico y semana. Resultados: los dos primeros pacientes por médico y semana estaban menos vacunados (7,9% frente a 12,5%, p = 0,021) y se confirmaron menos para gripe (53,6% frente a 66,4%, p <0,001), diferencias que se redujeron al ajustar por covariables. La efectividad de la vacuna calculada con todos los frotis fue del 49% (intervalo de confianza del 95% [IC95%]: 23-66%) y del 55% (IC95%: 27-72%) al analizar los dos primeros frotis semanales. Conclusión: la selección de los primeros pacientes semanales puede sesgar la efectividad de la vacuna antigripal, aunque en las temporadas analizadas este sesgo fue pequeño

Objective: to estimate the effectiveness of the influenza vaccine under different criteria for selecting patients for swabbing. Method: a case-control study was performed of laboratory-confirmed cases (n = 909) and negative controls for influenza (n = 732) in the 2010-2011 to 2012-2013 seasons in Navarre (Spain). The adjusted vaccine effectiveness was estimated by including all swabs from patients with influenza-like-illness and selecting only the first two cases per physician and week. Results: the first two patients per physician and week were less frequently vaccinated against influenza (7.9% vs. 12.5%, p = 0.021) and less often received confirmation of influenza (53.6% vs. 66.4%, p <0.001) than subsequent patients. These differences decreased after adjustment for covariates. The effectiveness of the influenza vaccine was 49% (95% CI: 23-66%) when all swabs were included and was 55% (95% CI: 27-72%) when we selected the first two swabs per week and physician. Conclusion: the selection of the first two patients per physician and week may bias assessment of the effectiveness of the influenza vaccine, although this bias was small in the seasons analyzed

[Influence of distinct criteria for selecting patients for swabbing on estimation of the effectiveness of the influenza vaccine]. / Influencia del criterio de selección de pacientes para la toma de frotis en la estimación de la efectividad de la vacuna antigripal.

OBJECTIVE: To estimate the effectiveness of the influenza vaccine under different criteria for selecting patients for swabbing. METHOD: A case-control study was performed of laboratory-confirmed cases (n=909) and negative controls for influenza (n=732) in the 2010-2011 to 2012-2013 seasons in Navarre (Spain). The adjusted vaccine effectiveness was estimated by including all swabs from patients with influenza-like-illness and selecting only the first two cases per physician and week. RESULTS: The first two patients per physician and week were less frequently vaccinated against influenza (7.9% vs. 12.5%, p=0.021) and less often received confirmation of influenza (53.6% vs. 66.4%, p <0.001) than subsequent patients. These differences decreased after adjustment for covariates. The effectiveness of the influenza vaccine was 49% (95% CI: 23-66%) when all swabs were included and was 55% (95% CI: 27-72%) when we selected the first two swabs per week and physician. CONCLUSION: The selection of the first two patients per physician and week may bias assessment of the effectiveness of the influenza vaccine, although this bias was small in the seasons analyzed.

Effectiveness of the monovalent influenza A(H1N1)2009 vaccine in Navarre, Spain, 2009-2010: cohort and case-control study.

We defined a population-based cohort (596,755 subjects) in Navarre, Spain, using electronic records from physicians, to evaluate the effectiveness of the monovalent A(H1N1)2009 vaccine in preventing influenza in the 2009-2010 pandemic season. During the 9-week period of vaccine availability and circulation of the A(H1N1)2009 virus, 4608 cases of medically attended influenza-like illness (MA-ILI) were registered (46 per 1000 person-years). After adjustment for sociodemographic covariables, outpatient visits and major chronic conditions, vaccination was associated with a 32% (95% CI: 8-50%) reduction in the overall incidence of MA-ILI. In a test negative case-control analysis nested in the cohort, swabs from 633 patients were included, and 123 were confirmed for A(H1N1)2009 influenza. No confirmed case had received A(H1N1)2009 vaccine versus 9.6% of controls (p<0.001). The vaccine effectiveness in preventing laboratory-confirmed influenza was 89% (95% CI: 36-100%) after adjusting for age, health care setting, major chronic conditions and period. Pandemic vaccine was effective in preventing MA-ILI and confirmed cases of influenza A(H1N1)2009 in the 2009-2010 season.