Immunomodulation of COVID-19 severity by helminth co-infection: Implications for COVID-19 vaccine efficacy

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an emerging virus in late 2019 causing coronavirus disease 2019 (COVID-19), has caused a catastrophic effect, resulting in an unprecedented global crisis. The immunopathology of COVID-19 appears to be clearly associated with a dysregulated immune response leading to organ failure and death. Similarly, over two billion people worldwide are infected with helminth, with those living in low-middle-income countries disproportionately affected. Helminth infections have been shown to possess immunomodulatory effects in several conditions. Helminth co-infection in COVID-19 patients is one of the potential reasons for global attention to answer why COVID-19 severity is still lower in helminth endemic countries. Recent studies have shown that helminth endemic countries showed fewer cases and deaths so far and helminth co-infection might reduce the severity of COVID-19. Moreover, lessons from other diseases with helminth co-infection have been shown to substantially reduce vaccine efficacy that could also be implicated for COVID-19. This immunomodulatory effect of helminth has intended and unintended consequences, both advantageous and disadvantageous which could decrease the severity of COVID-19 and COVID-19 vaccine efficacy respectively. Herewith, we discuss the overview of COVID-19 immune response, immunomodulatory effects of helminth co-infections in COVID-19, lessons from other diseases, and perspectives on the efficacy of COVID-19 vaccines.