key: cord-0759358-5ghua98e
authors: Wolday, Dawit; de Wit, Tobias F. Rinke
title: Response to Abdelrahman M et al commentary on “Parasites Protect from Severe COVID-19. Myth or Reality?”
date: 2022-04-09
journal: Int J Infect Dis
DOI: 10.1016/j.ijid.2022.04.012
sha: c18c6fe3e6c36ec7fd75341d4d7146f4dc004098
doc_id: 759358
cord_uid: 5ghua98e

nan

Dear Editor, In a recent correspondence, Abdelrahman et al. (2022) describe that the protective effect of parasites on COVID-19 to a myth rather than a reality (Bamorovat et al., 2021; Wolday et al., 2021a) . Additionally, they indicated that a study (Abdoli, 2020) has found that parasitic infections, like helminths, increase the risk of COVID-19 severity.

Concerning our study (Wolday et al., 2021a) , they noted that intestinal parasitic co-infection was attributed to having less COVID-19 complications. This is an incorrect interpretation as we in fact demonstrated that less COVID-19 complications were rather attributed to having preexisting co-infections with parasites and not vice versa. They incorrectly suggested that the probability of inclusion is associated with COVID-19 exposure and outcome (proportion of parasite co-infection). This is not the case, because in our study we defined exposure as having pre-existing parasite co-infection and outcome as the proportion of developing severe COVID-19. Moreover, admission bias in our cohort was minimal, due to the unique situation in our setting were all COVID-19 cases were followed, either quarantined in designated isolation hospitals or admitted to the intensive care unit (Abreha et al., 2021; Wolday et al., 2021a) .

Surprisingly, Abdelrahman et al. (2022) also incorrectly construed the publication by Abdoli (2020). A more careful review of this paper reveals a hypothesis that helminths may increase severity of COVID-19 and also may suppress the immune response to SARS-CoV-2 vaccines, but evidence was not provided. In contrast, our findings provide significant correlative evidence embedded in a sound immunological theory. Indeed, Bradbury et al (2020) were the first to propose that helminths may negatively impact the pathogenesis of COVID-19. An alternative 3 | 5 hypothesis was then suggested by Hayes et al (2020) that co-infection with helminths may indeed have a mitigating effect against severe COVID-19. Given that parasites have complex interrelationships with a host, and that different species and even different stages of parasite life cycle exerting differential immune responses in the host, we and others argued that parasitic coinfections could be either beneficial or detrimental to COVID-19 severity or their effects on SARS-CoV-2 vaccines (Gutman et al., 2020; Wolday et al., 2021b , Wolday et al., 2021c .

We suggest before concluding that co-infection with parasitic infection in reducing COVID-19 severity as being a "myth", it is imperative to provide evidence. Finally, we agree with Abdelrahman et al. (2022) that more evidence is required to ascertain in detail the causal relationship between parasitic infection and COVID-19 severity. 

None.

Not applicable. 

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