Draw a BPMN model with boundary event.

at any point after registration and before the vaccine is administered, the Vaccinee may realise that they had received the flu vaccine within the past 14 days (despite ticking the box earlier to say that they hadnt). In these cases, when s/he informs the relevant Vaccination staff member, the Vaccinees registration and confirmation of receipt of vaccine must be reversed, and s/he is advised to return after the 14 days since the flu injection have passed to start the process again.