You can give Syrup Calcimax P 5ml twice a day. Please expose to sunlight now if possible. Give lots of fruits and salads. Give home cooked fresh foods. Better to use Zincovit syrup at his age. The dose is 5ml once a day. In adults, zincovit capsules are used. Just dee daily dose at this age is 600 units. So give 3ml of justdee 800 iu per 5ml.

Normally also irrespective of pandemic, the wavelength at which vitamin D is absorbed from sun ( afternoon) , we do not expose our children without clothes in sunlight. So most of the children are deficient in vit D. Good nutritious diet with lot of fiber and proteins should be taken.