There are lots of articles going around at the moment that suggest certain diets and supplements can protect you from COVID-19. There is currently not enough evidence to support these claims.
In particular, there are claims that vitamin D will reduce your risk of coronavirus; again, there is not evidence to support this. We need vitamin D for our bones and muscles and we get most of it from sunshine and not from food. With many people self-isolating and not getting outside in the sunshine, they may not be getting enough vitamin D so it is recommended that they consider taking 10 micrograms of vitamin D per day (age 1 year and over).