Nurses at Waitakere Hospital dealing with Covid-19 patients were forced to change their protective wear up to eight times a shift, one of a suite of issues that may have led to staff catching the virus.
An report released this afternoon also found "usability" issues with the personal protective wear (PPE), and that was stressful for staff.
The Waitematā District Health Board has apologised to the staff - seven now have the virus - who were caring for patients from St Margaret's rest home.
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The report said the patients transferred to Waitakere Hospital in the middle of a "difficult, evolving and intense" situation.
Three of those patients have since died.
The report - with independent panel members including the chief nurse and midwifery officer at Waikato DHB and a NZ Nurses' Organisation representative - set out the chain of events that led to three nurses becoming infected.
It found the nursing staff provided exemplary care to the six patients on the ward; they were compassionate, professional and ensured the patients got the best care possible.
But the decision to transfer the residents was made quickly on a Friday and staff had a short time to plan and put together a Covid-ready ward.
The patients required full nursing care and deteriorated relatively quickly. Consequently, nurses needed to spend long periods of time at the patients' bedsides.
Full PPE was available to staff at all times. However, there were problems with usability and changes in types of PPE provided, which was stressful for staff.
And there was no way for nursing staff to communicate with staff outside the patients' rooms, which increased the frequency of donning and doffing PPE.
"It is well recognised that donning and doffing PPE, particularly doffing, is high risk for viral transmission, and it is therefore important to try and minimise the number of times this occurs," the report said.
"This needs to be balanced with the need to ensure staff are not exposed for prolonged periods unnecessarily in enclosed rooms with confirmed Covid-19 patients."
The report would be used to improve how similar situations were managed in future, deputy CEO Dr Andrew Brant said.
"We are deeply saddened that these nurses became infected with Covid. They were being selfless in caring for others in the middle of a difficult, evolving and intense situation at St Margaret's," he said.
"We recognise their professionalism in caring for patients from St Margaret's and we regret that they became ill in the course of their work."