Ah I understand better now :) Usually a pre-recruitment might involve checking immunity to thing like measles, mumps, rubella, hepatitis B, tuberculosis, chickenpox, diptheria, tenanus & polio. Basically any serious infectious disease that could potentially present a risk to a patient. Policies from different places are obviously not all the same, but in my work place if you can't prove you have had (or been vaccinated against) any of they above, they will check immunity via a blood test before employment commences. If any immunity test come back negative your friend may be offered the vaccine. Hope this is more helpful.