key: cord-0774410-7fsnd868
authors: Makram, Abdelrahman M.; Alied, Marcel; Khan, Zeeshan Ali; Huy, Nguyen Tien
title: Parasites Protect from Severe COVID-19. Myth or Reality?
date: 2022-03-22
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2022.03.027
sha: 2721a87bf3fc867250da9e2a4218bf000bf53227
doc_id: 774410
cord_uid: 7fsnd868

nan

with some parasitic diseases was identified (Gluchowska et al., 2021) . In this letter, we will elaborate 23 why we think that the protective effect of intestinal parasitic coinfection with COVID-19 could be a 24 myth. 25 One paper by Bamorovat et al. described, using case-control study design, how cutaneous 26 leishmaniasis can decrease the morbidity and mortality of COVID-19 (Bamorovat et al., 2021) . We 27 found that there are major concerns in the design of this study. Firstly, the authors included the 28 control group according to their "probable status of COVID-19 infection". Then, the authors would 29 dichotomize them according to the PCR test result into positive and negative (retrospectively). 30

Whereas the case participants were selected according to their "leishmaniasis" status and then 31 (prospectively) following them up to detect if they get infected with COVID-19. This leads to 32 selection bias (the criteria for inclusion in the case and control groups are different), differential 33 misclassification, and observer bias (a physician assessing the leishmaniasis patients can alter the 34 disease course). Moreover, the authors have not adjusted for any covariates in the study. 35

In another prospective cohort study, Wolday et al. suggested that intestinal parasitic co-infection 36 was attributed to having less COVID-19 complications (Wolday et al., 2021).We believe selection bias 37 is a major concern in this study because the authors included all patients screened for COVID-19 and 38 then tested them for parasites. So, the probability of inclusion is associated with the exposure 39 (COVID-19) and the outcome (proportion of parasite co-infection). There could also be admission 40 bias due to the selection from the screening program held at that time in Ethiopia. 41

Other case reports, animal studies, and reviews have claimed that some parasites can protect 42 against COVID-19 and other respiratory diseases (Hussein et al., 2020 , Mohamed et al., 2020 Accordingly, we believe that the evidence provided in the studies above may not support the 48 conclusion that parasitic co-infection can reduce the severity of COVID-19. And we believe that 49

further studies with better methodology should be conducted to discover the true impact of 50 parasitic co-infection in COVID-19 patients. 51

None. 56

Not applicable. 58

MA and NTH developed the idea. All authors contributed to the literature review and manuscript 60 writing. All authors approved the final version under the supervision of NTH. No one other than the 61 listed authors contributed to this work. 62

Prophylactic effect of cutaneous leishmaniasis against COVID-19: A case-control field assessment. Int 67

The New Status 69 of Parasitic Diseases in the COVID-19 Pandemic-Risk Factors or Protective Agents?

Malaria and COVID-19: unmasking their ties

COVID-19 unfolding filariasis: 74 The first case of SARS-CoV-2 and Wuchereria bancrofti coinfection

Helminth Modulation of Lung Inflammation

Potential 79 Influence of Helminth Molecules on COVID-19 Pathology