She is believed to have called at two addresses in last month claiming to be giving flu vaccinations.
In the first incident on Thursday 20 October 2011 the woman called at the home of a 63-year-old man who refused to let her into his house. On Thursday 3 November 2011 a woman called at the home of a 94-year-old Ripon woman and entered the house although it not thought that anything was stolen.
Neither of the people were given a flu vaccination or an injection of any kind.
In both cases, the woman is described as white, aged in her early 40s with blonde hair. She wore a blue dress similar in style to a nurse’s uniform and carried a orange plastic box.
PC Lorraine Diggins, of Ripon Safer Neighbourhood Team, said: “I have spoken with local health care providers and they have confirmed that this woman does not work for them and they never have staff making unannounced home visits.
“I would like to speak to anyone who may have been visited by this woman, and has not yet reported the incident, or can help to identify her and ask that they contact the police as soon as possible.
PC Diggins added: “I would like to remind homeowners that they should never let anyone into their homes unless they are absolutely certain the caller is genuine. Always ask them for proof of identity and contact the organisation they claim to be representing. A genuine caller will not mind waiting.
“If a homeowner would prefer not to answer the door to cold callers they should ask a neighbour if they are happy to verify a visitor’s identity and display a Nominated Neighbour poster, which can be downloaded from the force’s website, in a window near the door.”