According to medical reports those patients who died from Covid-19 coronavirus were the ones who had a vitamin D blood level of 15 ng/mL or less while those who survived had vitamin D blood levels of more than 30 ng/mL.
Vitamin D is essential for the functioning of the innate and adaptive immune system and vitamin D3 supplements are much more reliable.
Eventually they may come up with a safe and effective vaccine. But if you want to survive until then, you should use common sense and build up your immune system as this is all we have to defend ourselves apart from the normal social distancing, face mask and hand hygiene.
NB: Zinc 30 mg per day and magnesium 150 mg twice a day are also important cofactors to maintain a healthy immune system. I take this also every day.
If you want to research further, click on the links below:
Epidemic influenza and vitamin Dhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870528/
The role of Vitamin D in the prevention of Coronavirus Disease 2019 infection and mortality https://www.researchsquare.com/article/rs-21211/v1