Supplements containing vitamins C and D and other micronutrients, sometimes in amounts exceeding the federally recommended levels, are a safe, effective and low-cost means of helping your immune system fight off COVID-19 and other acute respiratory tract diseases – Oregon State University
Resources
https://www.eurekalert.org/pub_releases/2020-04/osu-dsa042320.php
https://www.mdpi.com/2072-6643/12/4/1181