key: cord-0877930-ompcqctu
authors: Sardinha, D. M.; Lobato, D. d. C.; Ferreira, A. L. d. S.; Lima, K. V. B.; Guimaraes, R. J. d. P. S. e.; Lima, L. N. G. C.
title: Analysis of 472,688 severe cases of COVID-19 in Brazil showed lower mortality in those vaccinated against influenza
date: 2021-05-14
journal: nan
DOI: 10.1101/2021.05.11.21257053
sha: faf8951d10161420a7fd3f53c899ed522c09e64d
doc_id: 877930
cord_uid: ompcqctu

Objective: To analyze the severe cases of COVID-19 in Brazil in 2020 and compare those vaccinated and unvaccinated against influenza in invasive ventilation, admission in Intensive Care Unit (ICU), and deaths. Method: Cross-sectional study with public data from the OpenDataSUS platform confirmed severe cases for COVID-19 in Brazil in the year 2020. Data were analyzed by SPSS, from the chi-square test of independence and binary logistic regression. Results: The population was 472,688 cases and 177,640 deaths, with lethality of 37.58% in severe cases. The test of independence was highly significant in vaccinated survivors (<0.0001), and regression showed an almost twofold odds ratio for invasive ventilation, ICU admission, and death in unvaccinated cases. Conclusion: We recommend mass influenza vaccination as an adjuvant in combating the COVID-19 pandemic in Brazil.

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) deaths, of which 66,868 were in the month of March 2021 alone, surpassing July 2020, which was the worst-case scenario in 2020 [3] .

Recently hypotheses have been raised that the trivalent influenza vaccine may be associated with lower severity and mortality in COVID-19. Some authors hypothesize that the association lies in sustained immunity, which is characterized by the recent stimulation of immune system responses to viral infections, which potentiated a better immune system response because it remains active through the toll-like receptor that is important for binding single-stranded RNA viruses, such as SARS-CoV-2. As well as cross-immunity, due to the structural similarities of the agents, such as the hemagglutinin protein [4, 5] . less likely to be admitted to the intensive care unit, 18% less likely to require mechanical ventilation, and 17% less likely to die [8] . A study in Italy analyzed data from vaccinated and unvaccinated elderly over 65 years of age, and showed moderate to strong negative correlation ( r = -.5874, n = 21, P = .0051), i.e., when there were higher rates of influenza vaccination, fewer deaths from COVID-19 occurred. [9] . Research by Yang et al [10] showed that COVID-19 patients who had not been vaccinated against influenza in the past year had a 2.44 (95% CI, 1.68, 3.61) higher chance of hospitalization and 3.29 (95% CI, 1.18, 13.77) higher chance of ICU admission when compared to those vaccinated. In this context, some hypotheses exist about other vaccines as a protective factor in mortality by COVID-19, as for example the BCG vaccine, the author highlights that BCG vaccination administered at birth can exert heterologous immune effects to increase protection against unrelated pathogens, besides protection against tuberculosis [11] . For O'Neill and Netea [12] , BCG vaccine has the potential to reprogram innate immunity, protecting against respiratory infections, because it is an attenuated vaccine administered as soon as the individual is born. Randomized studies have shown a 50% reduction in mortality in children vaccinated with BCG; thus, since most of the causes of death in children are respiratory infections, BCG vaccine has been associated with a reduction in deaths from all causes in children [13] . Thus, based on these hypotheses raised, our results may be associated with BCG protection, however our database for the analysis of this research did not have this information about BCG vaccination, only influenza, so the limitation of the study stands out.

Thus, our results from analysis of all severe cases of COVID-19 in 2020 in Brazil also associated that influenza vaccine reduces invasive ventilation, ICU admission and death, corroborated by some studies in the literature.

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We evidenced that the influenza vaccine is associated with a lower chance of ICU admission, invasive ventilation and death, although the immunological mechanisms responsible are still unclear in the literature, they are still hypotheses, however, the results of this research and other studies confirm this association of vaccination with better outcome in severe cases of COVID-19. We recommend that influenza vaccination be used as a secondary medicine to combat the pandemic of COVID-19, including individuals >6 months of age, as well as to ensure high vaccination coverage in the elderly population. To achieve this goal, influenza vaccine should be included in routine as an annual dose, regardless of specific influenza campaigns for the elderly and priority groups, as it will increase access and coverage. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) 

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