A efetividade da imunização na mortalidade de idosos com síndrome respiratória aguda grave por covid-19 no brasil: um estudo nacional de coorte retrospectiva

Abstract

The COVID-19 pandemic has underscored the vulnerability of the elderly, particularly to Severe Acute Respiratory Syndrome (SARS), due to comorbidities and a diminished immunological response. In Brazil, with an aging population, the vaccination campaign stands out. However, there is a lack of national studies on the effectiveness of vaccines in reducing mortality in this age group. This study is a retrospective observational cohort conducted nationally, focusing on elderly individuals hospitalized due to Severe Acute Respiratory Syndrome (SARS) associated with COVID-19, with their data recorded in the Influenza Epidemiological Surveillance Information System (SIVEP-GRIPE) for the period 2021/2022. The primary aim of the study was to analyze the occurrence of death within a 90-day period (Time-to-Event analysis). Analyzing 411,312 elderly (144,433 unvaccinated, 266,879 vaccinated), with an average age of 74.5 years and balanced gender distribution, the mortality rate was 43.9%, being lower in vaccinated (40.5%) versus unvaccinated (50.2%). Prevalent comorbidities included heart diseases (70.6%) and diabetes (51.3%). Vaccination showed a 26% reduction in the risk of death (IRR = 0.74) and a 19% increase in survival (HR = 0.81). Regionally, the North region had the lowest risk of death (IRR = 0.74), and the South, the highest (IRR = 0.88). Lower needs for invasive mechanical ventilation (OR = 0.68) and ICU admissions (OR = 0.88) were noted among vaccinated individuals. The effectiveness of vaccination improved with each additional dose, with the first dose (IRR = 0.92; HR = 0.95), the second dose (IRR = 0.85; HR = 0.87), and the booster dose (IRR = 0.64; HR = 0.73), all associated with significant improvements in reducing the risk of death and increasing survival, highlighting the importance of full adherence to the vaccination schedule. These data illustrate the importance of vaccination, including booster doses, in reducing mortality among the elderly affected by COVID-19. Significant differences were observed between vaccinated and unvaccinated groups, becoming more evident from the 30th day after vaccination, showing that vaccination decreased the risk of death by 26% among elderly patients, (IRR) of 0.74 (p<0,0000) after adjustments for variables such as age, sex, and comorbidities, and a 19% increase in survival for the same group (HR) of 0.81 (p<0,0000), suggesting that vaccination not only reduces the risk of death but also improves survival prospects for elderly patients hospitalized with the disease in a severe state. The results confirm the importance of vaccination as a vital public health tool, showing a significant association between immunization and reduced mortality in this vulnerable group. The crucial need for complete adherence to the vaccination schedule, including the application of booster doses, is emphasized, as the benefits of immunization intensify with the administration of subsequent doses