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How many New Zealanders haven’t caught Covid-19? – Expert Q&A

18 August 2022

University of Canterbury Professor Michael Plank says at least half of New Zealanders have been infected with Covid-19, while those who haven't are a "significant minority".


Professor Michael Plank

New Zealand’s second Omicron wave might just be easing up, with the latest data showing we seem to be in a downward trend. So are those who never got Covid-19 now in the minority?

The Science Media Centre (SMC) asked experts, including University of Canterbury Professor Michael Plank, about what the latest data says about rates of infection, what we still don’t know, and how this affects wider immunity to the virus. 

SDG-3-news-2023-uc.jpeg Sustainable Development Goal (SDG) 3 - Good Health & Well-Being

What do the data tell you about how many New Zealanders have or haven’t been infected?

"The true number of people who’ve had Covid-19 is unknown because we only know about cases who get tested and report their result. The proportion of infections that are reported is probably somewhere between 40% and 65%. It’s unlikely to be much less than 40% because at least 40% of all 20-25 year olds have already reported a case. On the other hand the reported infection rate is typically less than 65% of the infection rate in routinely tested cohorts such as border workers. This means it’s likely that at least half of New Zealanders have had Covid-19, although those that haven’t probably still represent a significant minority."

What does this mean for our herd immunity to Covid?

"The lack of an accurate estimate for the true number of infections creates uncertainty about how much immunity there currently is in the population. This makes it harder to estimate the potential size of future waves of Covid-19 or the impact of new variants. The best way to get an accurate picture of the true number of infections would be to systematically test a representative sample of the population on a regular basis. This would provide high-quality ongoing data about the level of Covid-19 in the community and reduce our reliance on self-reported test results."

Read the full article on the Science Media Centre here

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