How harmful for your health is a tuberculosis testing shot?

Intradermal shot: Tb testing shot (ppd test) is injected just under the most superficial layer of skin. It is done using a very thin & small needle & does not go too deep inside the skin. The discomfort is similar to that caused by a pin prick. After injecting ppd, there is tiny bump on the skin at that site which then can get bigger if your test is positive. Make sure you have it read within 48-72 hours after.

Nothing important: I would give its long term effect as being close to that of a mosquito bite. However. it could help find out you have a deadly disease, reduce it's spread and allow for a cure.