RESUMO
Vitamin D deficiency is associated with an increased risk of acute respiratory infection. There is an excess of respiratory infections and deaths in schizophrenia, a condition where vitamin D deficiency is especially prevalent. This potentially offers a modifiable risk factor to reduce the risk for and the severity of respiratory infection in people with schizophrenia, although there is as yet no evidence regarding the risk of COVID-19. In this narrative review, we describe the prevalence of vitamin D deficiency in schizophrenia, report the research examining the relationship between vitamin D levels and COVID-19 and discuss the associations between vitamin D deficiency and respiratory infection, including its immunomodulatory mechanism of action.