You don’t get UV this time of year unless you are far to the south... that’s why we need to consume foods with Vitamin D and / or take supplements as exposure to the son doesn’t provide that now.
Moreover, for “killing” a virus, the UV light is not going into the bloodstream and internal organs by going outside and getting some sunshine.
But it will kill the virus on your skin and your hair and your clothes. This is why shutting down the beaches this last summer was insanity. Also if you are in a crowd in the sunlight, you are safer than sitting alone in your apartment.