Northland health officials don't know how many flu cases there have been as only one GP practice is regularly reporting them, with some arguing it made it difficult to see if the immunisation campaign was having any impact.
However, health officials said if there was a "significant event", like a flu outbreak, they would find out through other avenues, despite the lack of data.
There have been 46 hospital admissions from influenza in Northland since May, with three requiring time in intensive care. However, it was unclear how many more cases there have been which have not required hospital admission because of the lack of GP reporting.
"Unfortunately, limited Northland practices are included in the surveillance which means we have limited Northland community specific data," a Northland District Health Board spokeswoman said.
Northland medical officer of health Clair Mills said out of the 41 practices in Northland, only one in Whangarei had signed on. That was up from zero reporting last year, with the highest in the past being four or five practices- but usually in a same area. She said the region's consistently low numbers had been "a bit embarrassing".