An Auckland high-school teacher was ‘gobsmacked’ when she tested Covid positive for the second time in two months.
Tanya Glengarry told 1News that she was set to go out, before taking the test.
"I had forgotten all about it and I thought ‘oh I better check it.’
"I probably thought I was a little bit safer from getting it again, but apparently not."
Otago University Biochemistry Professor Kurt Krause says the phenomenon of catching Covid twice is becoming increasingly common.
"We had a sense that immunity might last 6 months or a year, but it turns out immunity to Covid infection is pretty variable."
Royal New Zealand College of GPs director, Dr Bryan Betty, says the reason for the confusion comes down to the way people test.
"There are a lot of false positive cases occurring because you have residual viruses in the nasal passages.
"The approach you need to take if you do develop symptoms within that three-month period, stay home… it could be the flu, it could be a cold, but it's unlikely to be covid again," he said.
In a statement, the Ministry of Health said it’s monitoring re-infection rates, which could be linked to a range of factors including waning immunity, a mild first infection or testing positive for a different variant.