Chickens: Do you Vaccinate Your Small Flock of Birds?

[Henlus]

How do you divide it accurately?

Thanks for your contributions so far. I was thinking that if you have let's say 10 birds and 200 doses of vaccine (live vaccine). You add a little water to the vaccine to dissolve it. Then using a syringe, you get the volume of the vaccine solution to be 3ml. Then you do a little mathematics:
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If 200 birds need 3ml of vaccine, then 10 birds will need less than that, so more should divide: 10/200 x 3ml = 0.15ml. So you give the birds slightly more than 0.15ml of the vaccine solution. What do you think?