In this retrospective, single-center, observational study with inpatients with COVID-19 in Madrid, Spain, a better outcome, in terms of lower risk to moderate or severe ARDS, was observed among IC as compared to non-IC. A trend, albeit non-significant, toward a longer time to moderate-severe ARDS, a lower need for MV/NIV, and shorter hospitalization was also detected. A comparison of both groups observed no differences were observed in the death ratio.
Immunosuppression has been widely considered a risk factor for infections, with a higher incidence and a worse outcome, including those caused by a respiratory virus9. For example, influenza infection was observed to be associated with a higher risk of more hospitalizations, a longer length of virus shedding, a more severe disease, and complications requiring intensive care and MV10. Additionally, several studies consider immunosuppression to be a risk factor of a more severe disease in MERS-CoV infection11-14. Previous works have already described risk factors predicting a worse outcome in COVID-19 patients, such as older age3, 15-17, comorbidities (hypertension, diabetes, or vascular diseases)3, 15, 17, -and laboratory findings, with special attention paid to those indicating hyperinflammation or cytokine storm syndrome18, 19, like elevated serum D-dimer, ferritin, C-reactive protein, or interleukin (IL)-6 levels3, 15-17. Nevertheless, none of these works has specifically assessed immunosuppression as a risk factor in COVID-19 patients. A recent population-based study in China evaluated cancer patients with recent surgery or chemotherapy, and found a higher risk of severe events20, while newly released data detected a 3.7x lower risk of intensive care unit (ICU) admission among IC patients compared to viral pneumonia21. In our study, a lower proportion of IC patients developing moderate or severe ARDS was observed, with a trend toward a longer time to event. We decided to assess this variable as a primary endpoint due to its higher specificity in detecting more inflammatory patients. To delve into a possible pathology or drug explaining these results, we further differentiated IC patients between those with an AD and those with other diseases (such as cancer or an organ transplant). However, both cohorts showed similar results, suggesting the immunocompromised state itself confers the protective effect. In line with this result, a trend toward a lower risk of MV/NIV, a composite of the need for MV/NIV or death, and a shorter length of hospitalization were also detected, probably due to the lower risk of ARDS.
This data might be explained by pathophysiological findings, such as the three-stage classification model of SARS-CoV-2 infection proposed by Siddiqi et al.4, with two distinct but overlapping subsets. The first triggered by the virus itself and the second, occurring in a minority of patients, host-mediated and based on an excessive immune response, leading to ARDS, the need for MV, and, potentially death3, 16-18. Pathophysiology similar to that of SARS-CoV has been hypothesized for SARS-CoV-2 infection22, in which a marked elevation of cytokines of the Th1 cell-mediated immunity (such as interferon (IFN)-g, IL-1, IL-6, and IL-12) and hyperinnate (neutrophil chemokine IL-8, monocyte chemoattractant protein-1 (MCP-1), and Th1 chemokine IFNg-inducible protein-10 [IP-10]) inflammatory response23 have been observed. For this reason, several immunomodulatory drugs, such as corticosteroids, intravenous immune globulin, and cytokine inhibitors, have been proposed depending on whether the hyperinflammation stage is suspected18, 19, 22. Preliminary data suggest a potential benefit of methylprednisolone in terms of the risk of death after the development of ARDS3, though clinical trials are required before recommending this therapy. All these results support, in line with other authors’ opinions5 and recent data21, the notion that immunosuppression might confer a protective effect in the most severe stages of the disease.
No differences in death rate were observed in our cohort. The reasons for these results might be explained by the smaller sample size of patients with a final outcome, the short follow-up, or unknown confounding factors. For example, during cytokine storm syndrome, ARDS is not the single inflammatory complication observed, as evidence of multi-organ dysfunction, with acute cardiac injury24 and liver and renal impairment3, 16, 17, 25 , has been described. This might be attributable to the widespread distribution of angiotensin converting enzyme 2 —the functional receptor for SARS-CoV-2— in multiple organs26. In addition, the results may be biased by the fact that IC patients might never get to mechanical ventilation, being considered too frail or disabled, so they are more likely to die than non-IC patients. Also, several factors related to the development of ARDS that were not associated with death have been described3, which indicates that different pathophysiological changes –from hospital admission to the development of ARDS and from the development of ARDS to death- may exist.
Thus, our results might have relevance in terms of establishing recommendations for physicians treating IC patients. Discontinuation of immunosuppressive drugs may have implications with respect to diminishing the underlying disease control, with potential fatal outcomes in either cancer or organ transplant patients or the reactivation27 or even rebound28 of disease activity among autoimmune disorders. Taking into account this data, careful individual decision-making about maintaining immunosuppressive drugs in COVID-19 patients must be performed. Second, less aggressive anti-inflammatory management among IC patients might be contemplated, lowering the risk of bacterial co-infections. Third, social and preventive care recommendations might be reconsidered for these patients.
This study has several limitations. First, a potential selection bias might have occurred, as only hospitalized (outside of ICU) patients were evaluated and IC might be admitted more easily by its own condition than non-IC. To diminish this bias, all consecutive admitted patients were selected. Second, this study was conducted at a single center with a limited sample size. Third, due to the lack of evidence-based treatment protocols, the treating physicians took different management approaches (especially with anti-viral drugs or corticosteroids), which could have altered the development of the outcomes. Fourth, the retrospective character of the study and the short follow-up time warrant caution in interpreting the data. Further studies with a prospective design and a larger sample size, including outpatients, might gain a better understanding of the role that immunosuppression plays among COVID-19 patients.
In conclusion, in our cohort immunosuppression was associated with a lower risk of moderate or severe ARDS, a trend toward a reduced need for MV/NIV, a shorter hospitalization and a longer time before moderate or severe ARDS occurs. We found the mortality rate was not increased in IC patients. This reinforces that there is a potential protective effect of immunosuppression against a possible hyperinflammation host response observed in SARS-CoV-2 infection and warrants reconsideration of the decision to discontinue immunosuppressive drugs in patients with severe underlying diseases and the management of these diseases during infection.