NZ needs 97% vaccination rate for herd immunity against most infectious Covid-19 variants

Source: 1News

New modelling shows 97 per cent of Kiwis need to be vaccinated against Covid-19 before New Zealand can achieve herd immunity from the most infectious virus variants and remove public health restrictions.

That’s according to a study led by a Victoria University epidemiologist.

The modelling was carried out by Te Pūnaha Matatini scientists who found that the number of Covid-related hospitalisations and deaths would drop significantly once 75-80 per cent of people are vaccinated, however reaching herd immunity against more infectious variants would require a much higher vaccination rate.

But given the Pfizer vaccine is still only approved for New Zealanders aged 12 and over, vaccinating 97 per cent of the population is not currently possible. 

The scientists felt measures such as masks, alert levels and border restrictions needed to remain in place for the vaccine roll out.

Massey University's Professor Mick Roberts agreed mask-wearing, testing and tracing will be necessary for some time. He said the only way to achieve herd immunity — without having a major outbreak — is by achieving a high level of vaccination coverage.

"The concept of herd immunity means that, on average, each infected person would infect less than one other person, and therefore a major outbreak would be prevented," he explained.

University of Canterbury's Associate Professor Malcolm Campbell said even once people are vaccinated, they still need to carefully think about following public health messages and measures.

He said health authorities needed to vaccinate as many people as they could, at least four out of five, to get to herd immunity. 

Meanwhile, both Te Pūnaha Matatini and National Hauora Coalition's Dr Rawiri McKree Jansen noted Māori communities would remain vulnerable to major outbreaks if they had "relatively low vaccine coverage" or "high contact rates".

Jansen felt Māori communities were exposed to both of these risks at the moment as the vaccination programme was underperforming on the equity front.

"The paper is a timely provocation to ensure that a pro-equity vaccination programme is resourced.

"Until vaccination rates in the order of 90 per cent of eligible Māori are achieved, opening of the borders would likely be catastrophic."

Woman seen wearing a mask

University of Auckland's Andrew Sporle felt similarly. 

"This new modelling demonstrates how important it will be to protect those at higher risk of infection and poor outcomes as the vaccine rollout continues," he said. 

"We already know that Māori and Pacific people have had much worse outcomes from the current epidemic. Those populations also have much larger proportions of their population who aren’t old enough for vaccination or who have pre-existing conditions.

"While improving the vaccination coverage for Māori and Pacific adults needs to be urgently addressed, there also needs to be increased support for local initiatives to protect local communities and improving contact tracing in case of an outbreak."

As of June 22, 61,294 Māori have received a first dose of the vaccine, while 36,283 have received their second dose.

As of June 22, 637,847 Kiwis have had their first doses of the vaccine, while 381,517 people have had their second doses.

This is a total of 1.02 million.