But the Ministry couldn't say how they were infected - whether it was a patient or colleague - though acknowledged "the importance of understanding where and how people contracted Covid-19."
"We continue to work to broaden our understanding and collate this information, so we can continue to keep New Zealanders safe," it said in a statement.
ESR, which operates the national notifiable disease surveillance database, EpiSurv, on behalf of the Health Ministry, could only break down infection sources into:
• close contacts of a locally acquired case with an unknown source (95),
• totally unknown source (8)
It's understood the infection source would have been recorded but it's not easily pulled or collated from the data systems it uses.
Resident Doctors' Association national secretary, Deborah Powell, said that the Ministry couldn't provide data on how healthcare workers were infected "simply isn't good enough".
"We've failed them and we need to know why."
One of the measures of success in fighting the virus should have been ensuring healthcare workers were protected, and without the data that was impossible to gauge, said Powell.
"I am incredibly disappointed that the data isn't available.
"Not all of them would have contracted Covid in the workplace, that's why not collecting that data is so difficult. Twelve per cent is a really high figure and we think we need to know more about this."
The fact 75 per cent of the infected healthcare workers were women reflected the fact the majority of the health sector's workers were women, said Powell.
Under the Health and Safety at Work Act workers are entitled to work in environments where health risks are properly controlled.
Kerri Nuku, of the NZ Nursing Organisation, is disappointed the Ministry of Health can't say how healthcare workers were infected at work. Photo / Paul Taylor
The Nurses Organisation Kaiwhakahaere Kerri Nuku said employers had obligations to keep their staff safe and the "critical" data should be easily accessible so it could be learned from.
District Health Boards and the Ministry needed to know how frontline healthcare workers were infected in order to prevent it happening again.
"I'm just astounded actually to be quite honest. I guess I'm speechless because I'm disappointed. All along the catchcry has been 'Be safe, feel safe' and we've had to take comfort to that."
Nuku said there was also "information missing" about how many healthcare workers needed to be stood down or go into isolation after coming into contact with a Covid-19 case.
The DHB's investigation only looked into three nurses' infections and was neither independent nor robust, Powell said.
WorkSafe said its role as a health and safety regulator "generally doesn't involve investigating the spread of infectious disease".
But it intended to conduct a review of the whole regulatory framework to "ensure the most appropriate agency intervenes when it comes to matters involving the public health sector".
Director general of health Ashley Bloomfield said it surprised him the data on health workers' infections wasn't available as the Ministry had previously reported on healthcare workers who'd been infected in their workplace.
On April 15, the Ministry found of 107 healthcare workers, 46 were infected by an exposure to a patient or colleague. But that information has ceased to be reported.
Health Minister David Clark said he'd ask the Ministry for the latest figures and expected them to be "working very carefully through these details" and "learning lessons as they go".
He was asked whether he thought it was a health and safety issue but did not respond to the question.
