If it was me I would be basing my decision on the risk to the young person. If the risks are tolerable/low as they seem to be from your post then a refresher would be the way I would go, possibly with specific reference to your full induction done less than a year ago. In my business I woud focus on MHO retaining, Fire safety, slips, trips and falls, housekeeping (i.e. close filing cabinets after use) giving other areas such as workplace transport and COSHH little or no focus. The key thing is to ensure good supervision from a competent person. Hope this helps.