Mantoux is not a straightforward immunisation.  It has never been licensed and the manufacturers have no intention of paying to get it licensed.  Therefore special rules apply.  The Medicines and Healthcare Products Regulatory Agency have clarified the procedure in an email to me dated 27/05/2015 as follows:

We understand that Mantoux is an unlicensed medicinal product.  Legally, an unlicensed medicine must be ordered by a doctor or other eligible independent prescriber (eg nurse independent prescriber) for individual patients on his/her own responsibility. The doctor is therefore responsible for the decision to give the unlicensed vaccine for the individual concerned.  He or she needs to authorise the administration and this could be via a patient specific direction covering a number of patients.  However, the directions must be for named patients.  An authorisation page with names subsequently added by someone else would not be sufficient. 

In relation to similar enquiries, we  have also advised that the prescriber must have adequate knowledge of the patient's health, and be satisfied that the medicine to be administered serves the individual needs of each patient on that list.

The same considerations apply to other independent prescribers such as nurses and pharmacists using unlicensed products.

So in summary, OH services providing Mantoux should prepare a list of patients needing Mantoux.  This should then be signed (or otherwise authorised) by a doctor or eligible independent prescriber.  You can’t have a blank sheet signed, and add names later.

It is likely to be reasonable to have a robust policy for assessing those needing Mantoux to ensure adequate knowledge of the patient’s health and to ensure it serves a need.  The nurse can add their names to a list formatted as a Patient Specific Directive.  This can then be signed by an OHP.  If necessary the list can be emailed to the OHP, and the email reply can be the authorisation.