A Covid-19 vaccine advisor is warning people not to get multiple Pfizer doses in a day.
The Ministry of Health is investigating reports of a man seeking 10 jabs in a day, for money.
University of Otago Professor Peter McIntyre calls it 'foolish' behaviour.
"Firstly it's unlikely that would be successful ultimately and secondly you're putting yourself at risk of adverse effects, so on both sides of the coin a dumb thing to do."
McIntyre said anyone deliberately having extra doses in a day is at much higher risk of serious adverse side effects.
"It's a long way past the recommended upper limit, even if you are a big male and although severe side effects are rare, you would increase your chances from rare to a bit less than rare which is not a great thing to do."
The Ministry of Health says medical practitioners operate in a high-trust environment, relying on good faith.
It advises anyone who has had more doses of Pfizer than recommended to seek clinical advice as soon as practicable.