No matter whether meat eaters or vegans - a vitamin D deficiency can occur in any diet. Your body is able to synthesize effective vitamin D from the precursors of the vitamin you ingest through your diet. It can also produce vitamin D through exposure to the sun (UV-B).
You need vitamin D for strong teeth and bones and an intact immune system. Symptoms of undersupply include increased susceptibility to infections, an increased tendency to allergies, fatigue and depression.
In order to prevent a vitamin D deficiency as a non-vegan or vegan,
longer walks and outdoor activities are highly recommended. In addition, you can cover your needs with fortified foods or dietary supplements. Vitamin D3 preparations are particularly recommended. If these were won until some years ago only from animal fat, they exist by now also vegan. Vitamin D3 is made from lichen. For higher doses of vitamin D3 an additional intake of vitamin K2 is recommended, which is also available as a vegan preparation.