Risk and Protective Factors for COVID-19 Morbidity, Severity, and Mortality

Abstract

The outbreak of the coronavirus disease 2019 (COVID-19), caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become an evolving global health crisis. Currently, a number of risk factors have been identified to have a potential impact on increasing the morbidity of COVID-19 in adults, including old age, male sex, pre-existing comorbidities, and racial/ethnic disparities. In addition to these factors, changes in laboratory indices and pro-inflammatory cytokines, as well as possible complications, could indicate the progression of COVID-19 into a severe and critical stage. Children predominantly suffer from mild illnesses due to COVID-19. Similar to adults, the main risk factors in pediatric patients include age and pre-existing comorbidities. In contrast, supplementation with a healthy diet and sufficient nutrition, COVID-19 vaccination, and atopic conditions may act as protective factors against the infection of SARS-CoV-2. COVID-19 vaccination not only protects vulnerable individuals from SARS-CoV-2 infection, more importantly, it may also reduce the development of severe disease and death due to COVID-19. Currently used therapies for COVID-19 are off-label and empiric, and their impacts on the severity and mortality of COVID-19 are still unclear. The interaction between asthma and COVID-19 may be bidirectional and needs to be clarified in more studies. In this review, we highlight the clinical evidence supporting the rationale for the risk and protective factors for the morbidity, severity, and mortality of COVID-19.

Keywords: Asthma; COVID-19; Comorbidity; Protective factors; Risk factors; SARS-CoV-2.

Fig. 1

Part of the protective and risk factors of COVID-19. Healthy diet, sufficient nutrition, atopic conditions, and COVID-19 vaccination are protective factors against the infection and development of COVID-19. Increased anti-inflammatory cytokines and decreased ACE2 expression may contribute to the protective effect of these factors. Also, induction of antibody response and T-cell activation by COVID-19 vaccination may also help in avoiding the infection, progression, and poor clinical outcome. On the contrary, old age, male sex, pre-existing comorbidities, and racial/ethnic disparities are risk factors for the morbidity of COVID-19. In addition, increases in the several laboratory indices and pro-inflammatory cytokines, as well as possible complications, could indicate the progression of COVID-19 into a severe and critical stage. Elevated expression of ACE2 and TMPRSS2, as well as the increase of pro-inflammatory cytokines, may underlie the predisposition. ACE2, angiotensin-converting enzyme; TMPRSS2, transmembrane protease serine 2