The concurrent timing of the COVID-19 pandemic and the seasonal occurrence of influenza, makes it especially important to analyze the possible effect of the influenza vaccine on the risk of contracting COVID-19, or in reducing the complications caused by both diseases, especially in vulnerable populations. There is very little scientific information on the possible protective role of the influenza vaccine against the risk of contracting COVID-19, particularly in groups at high-risk of influenza complications. Reducing the risk of contracting COVID-19 in high-risk patients (those with a higher risk of infection, complications, and death) is essential to improve public well-being and to reduce hospital pressure and the collapse of primary health centers. Apart from overlapping in time, COVID-19 and flu share common aspects of transmission, so that measures to protect against flu might be effective in reducing the risk of contracting COVID-19. In this study, we conclude that the risk of contracting COVID-19 is reduced if patients are vaccinated against flu, but the reduction is small (0.22%) and therefore not clinically important. When this reduction is analysed based on the risk factor suffered by the patient, statistically significant differences have been obtained for patients with cardiovascular problems, diabetics, chronic lung and chronic kidney disease; in all four cases the reduction in the risk of contagion does not reach 1%. It is worth highlighting the behaviour that is completely different from the rest of the data for institutionalized patients. The data for these patients does not suggest a reduction in the risk of contagion for patients vaccinated against the flu, but rather the opposite, a significant increase of 6%. Socioeconomic conditions, as measured by the MEDEA deprivation index, explain increases in the risk of contracting COVID-19, and awareness campaigns should be increased to boost vaccination programs.

The concurrent timing of the COVID-19 pandemic and the seasonal occurrence of influenza, makes it especially important to analyze the possible effect of the influenza vaccine on the risk of contracting COVID-19, or in reducing the complications caused by both diseases, especially in vulnerable populations. There is very little scientific information on the possible protective role of the influenza vaccine against the risk of contracting COVID-19, particularly in groups at high-risk of influenza complications. Reducing the risk of contracting COVID-19 in high-risk patients (those with a higher risk of infection, complications, and death) is essential to improve public well-being and to reduce hospital pressure and the collapse of primary health centers. Apart from overlapping in time, COVID-19 and flu share common aspects of transmission, so that measures to protect against flu might be effective in reducing the risk of contracting COVID-19. In this study, we conclude that the risk of contracting COVID-19 is reduced if patients are vaccinated against flu, but the reduction is small (0.22%) and therefore not clinically important. When this reduction is analysed based on the risk factor suffered by the patient, statistically significant differences have been obtained for patients with cardiovascular problems, diabetics, chronic lung and chronic kidney, in all four cases the reduction in the risk of contagion does not reach 1%. It is worth highlighting the behaviour that is completely different from the rest of the data for institutionalized patients. The data for these patients does not suggest a reduction in the risk of contagion for patients vaccinated against the flu, but rather the opposite, a significant increase of 6%. Socioeconomic conditions, as measured by the MEDEA deprivation index, explain increases in the risk of contracting COVID-19, and awareness campaigns should be increased to boost vaccination programs.

Describir la incidencia y mortalidad de COVID-19, durante la primera ola, en la población de personas mayores de Barcelona, según sus niveles previos de fragilidad. Estudio de cohortes retrospectivo. Población de 65 o más años asignada a los centros de Atención Primaria de Barcelona del Institut Català de la Salut, seguidos entre marzo y junio de 2020. Fragilidad calculada al inicio a partir de la historia clínica informatizada. Resultados durante el seguimiento: diagnóstico de COVID-19, posible o confirmado con PCR y mortalidad por todas las causas. Se analizaron 251788 mayores de 64 años. Un 61,3% tenían algún nivel de fragilidad, 27,8% moderada o grave. La incidencia de COVID-19 fue de 3,13 casos por 100 habitantes (N = 7883) y la mortalidad por COVID-19 fue del 21,5% (N =1 691). Tanto la incidencia como la mortalidad por COVID-19 fueron superiores a mayor edad, en hombres, a mayor privación y a mayor nivel de fragilidad. Los individuos con fragilidad leve, moderada y grave tuvieron un hazard ratio ajustado de enfermedad por COVID-19 de 1,47, 2,08 y 3,50 respectivamente. Entre los sujetos con COVID-19, aquéllos con fragilidad leve, moderada y grave tuvieron un hazard ratio ajustado de mortalidad por COVID-19 de 1,44, 1,69 y 2,47 respectivamente. Consideramos necesario el abordaje de la fragilidad también en situación de pandemia, dado que es una condición tratable y a su vez factor de riesgo de COVID-19 más grave, donde el papel de la Atención Primaria es primordial, por su accesibilidad y longitudinalidad.