Private medical notes about 90 patients - including details of a woman suffering mental illness after childbirth - were stolen from a social worker's car.
The incident has sparked a warning for health workers to keep patient notes in secure containers.
Counties Manukau District Health Board chief executive Geraint Martin has posted a blog post to health professionals advising them of their legal responsibility to protect patients' sensitive files when moving among hospital, clinics or homes.
After the theft two years ago, one patient complained to the Privacy Commissioner. In a bid to avoid litigation the commissioner and Martin have agreed on a plan for the DHB to increase care of patient files.
In an online message to staff senior legal adviser John Hanson wrote: "If possible, transport notes or information in a secure container and remain in touch with them. They should never be left in open view or on a seat." Staff travelling with patient files on a windy or rainy day should "secure the notes in a bag, so they don't blow away or get wet".
Privacy Commissioner John Edwards told the Herald on Sunday that health professionals had to be accountable.
"With more health services being delivered in the community and the need for clinicians to be out and about, this increases the risk and therefore heightens the need to be vigilant about what information they are taking and how it is secured," he said.
In January, sensitive health documents spilled on to an Auckland motorway after a staff member left them on top of a car. They were picked up by a member of the public.