The global health crisis as a result of covid-19 demands fast and efficient response from global health care system. The evidence of nutrition-based interventions for viral diseases from past clinical trials, and its importance for optimizing the host immune response was reviewed in this paper. The immune system has involved in the protection of the host from pathogenic organisms, communicating molecules and functional responses. It is a known factor that nutrition plays key role in supporting the immune system as the role of nutrients feature prominently in a number of scientific literatures. Several clinical data showed that micronutrients like vitamins, including vitamins A, B6, B12, C, D, E and folic acid; trace elements including, zinc, iron, selenium, magnesium, copper and the omega-3 fatty acids like EPA & DHA play a major role in supporting the immune system. Inadequate intake of these nutrients is widespread resulting to a decreasing in resistance to infections and an increasing in diseases burden. Regarding the COVID-19 pandemic, the roles of nutrition for strengthening immune system for the patients to have strong resistant against the virus is also considered in this paper. It is believed that COVID-19 increases its severity or a host is susceptible to infectious disease once the immune system does not function optimally.

Summary: Vitamin A is an essential micronutrient needed by the body for various physiological functions. Its deficiency is associated with several functional disorders. The objective of this study is to determine blood vitamin A levels in malnourished and healthy children. Methods: It is a cross-sectional analytical study, consisting of determining the vitamin A content in the blood of children suffering from malnutrition and those in good nutritional status. Our sampling was casual and 59 children aged 6 to 59 months were retained. Among them 30 healthy children chosen from those attending preschool consultation at U HC and 29 malnourished children from those followed at M TNU for the management of malnutrition. The serum vitamin A assay was performed according to the method described by Tietz. Children with serum vitamin A level below 30 μg / 100 ml had vitamin A deficiency and those with a serum level greater than or equal to 30 μg / 100 ml had good vitamin A status. Percent, average and standard deviation calculations were performed. The Chi square statistical test was used to compare serum vitamin A content in healthy and malnourished children, as well as other maternal parameters for a significance level of 0.05.  Results: from 59 children examined, 30 or 50.8% were 6-17 months old, the average age was 21.9 ± 13 months. 45.7% had a serum retinol level between 50-59 μg/100 ml; the average value was 46.84 μg ± 14.27.  The prevalence of VAD was 20.3% and this deficit was more marked in children aged 6-17 months that is 50% (P<0.014). Among 12 children with VAD, 10 or 83.3% were the wealthy and two were the malnourished, the difference was statically significant (P< 0.011). Conclusion: Vitamin A deficiency remains a major health problem in the DRC. This affect all children regardless of their current nutritional status. Supplementation with this vitamin remains one of the palliative solutions.