I don’t have personal experience with this situation, but if you have their vaccine record far enough in advance, see if the staff member can at least start the missing series in their home country before leaving for the US. Odds are good it will be much less expensive that way. They may have better luck if they can show proof the vaccines are required for work. Otherwise, they could schedule vaccines with a pharmacy in the US, but that could get pricy quickly, even using privately owned pharmacies. Your local health department *might* be able to offer them, but they may be restricted by age or residency rules.
If you decide to waive the requirement for certain vaccinations, be sure your health staff is aware, because they will need to include them in their differential diagnoses if there are issues. You would also need to consider how waiving those requirements could impact others, particularly any immune-compromised campers or staff. I hope this is somewhat helpful.