Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search

 

When Will New Zealand Have Herd Immunity?

The trans-Tasman bubble has been a step closer to normality with some semblance of overseas travel returning. Since then our borders have been shutting and re-opening to Australian states as new cases of Covid-19 emerge in their cities. This is not normality. With the emergence of the highly infectious delta variant threatening to pop the bubble completely, just how long will it be before things go back to normal for good?

Te Pūnaha Matatini scientists say four in five Kiwis need to get the jab before we can stop worrying about lockdowns and alert levels and start opening up again to the rest of the world. Until we hit this number, the modellers say that public health measures will be needed throughout all of our vaccine rollout to avoid deaths and serious illness.

The Government hopes to have most people vaccinated by the end of the year, but this will depend largely on compliance.

Lead author of the study, Nic Steyn says that the good news is increasing levels of vaccination will make maintaining an elimination strategy easier and allow the country to eventually move from relying on population-wide interventions like lockdowns to more targeted controls like contact tracing in the later stages of the rollout.

“We’re going to need to use the vaccine in conjunction with the other layers of protection that we have at the moment,” says Professor Michael Plank.

“This means that border restrictions, the Alert Level system, community testing and contact tracing will need to remain in place.”

The team used an age-structured model of COVID-19 transmission in Aotearoa New Zealand to estimate how increasing levels of immunity through vaccination can slow the growth of an outbreak. The models combined the latest available data on vaccine effectiveness with social contact survey data that estimates how much contact there is between people in different age groups across the country.

This modelling provides an indication of the potential for spread at a broad-scale national level and includes a range of scenarios at various stages of the vaccine rollout, from contained local outbreaks to an unmitigated epidemic.

Professor Shaun Hendy says that we’re still vulnerable to COVID-19 and will remain vulnerable even once the vaccine rollout is complete, but the results show that things will get better as the rollout progresses.

This modelling also includes the first New Zealand-specific estimates of the percentage of the population that needs to be vaccinated to reach population immunity. The lowest estimate of the population immunity threshold that the models produced was an 83% vaccination rate across the total population.

This was based on data from older variants of the virus with an estimated basic reproduction number of 4.5 and assuming the vaccine reduces transmission by 85%. Emerging data on newer more transmissible variants suggests a higher threshold, although this remains uncertain.

“Until we get close to that threshold we are still at risk of a significant health impact from an outbreak that would include overwhelming our healthcare capacity,” says Hendy.

“While the rollout is still underway, the elimination strategy gives us the best options for controlling any outbreaks and protecting people who haven’t yet been vaccinated.”

Vaccination rates will vary across Aotearoa New Zealand, so even if population immunity is reached nationally, communities with vaccination rates lower than the national average will remain at risk of hospitalisation and fatalities from COVID-19 outbreaks. Further modelling work will be needed to investigate this.

Professor Michael Plank cautions that we’re not going to one day magically hit a population immunity threshold where we can open the borders and everything goes completely back to normal. It will be more of a gradual relaxation of border measures alongside continued testing and contact tracing measures.

“If we relax border restrictions, we will see COVID-19 cases and it’s quite likely that we’ll see outbreaks. The way to protect against those outbreaks is to get vaccinated.”

There is still a lot to learn about the Pfizer vaccine and its effectiveness in different population groups. These models will need to be updated as new data is collected internationally about vaccine effectiveness and transmissibility of new variants.

Plank says that these results deliver a clear message: As more of the population gets vaccinated, we still need to go as hard as we’ve ever done on testing, contact tracing, scanning in, hand sanitising and wearing masks.

“The vaccine rollout is good news, but life is not going back to normal for some time,” says Hendy.

Immunisation Advisory Centre’s Professor Peter McIntyre points out a limitation of the study is that it looks at a scenario that is very unlikely in practice – opening up the border without restrictions and modelling on five infected people entering daily for two years.

“The actual situation will almost certainly be that borders will open only in the context of high vaccine coverage and include entry conditions such as pre-testing and proof of vaccination status – this will give much more favourable outcomes than the authors suggest,” says McIntyre.

“We would like to see further refinement of this valuable model and its assumptions to better reflect the lowered risk of severe disease when there is high vaccine coverage in New Zealand and borders are cautiously opened to limited arrivals.

“This should better reflect the real-world experience of countries such as the UK and Israel, within the context of some community transmission and taking into consideration the reduction in severity of cases occurring in vaccinated people due to breakthrough infections.

“We can be confident that severe cases will be uncommon in a high vaccine coverage future.”

© Scoop Media

 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

Government: Northland To Move To Orange, NZ Prepared For Omicron


Northland will move to Orange at 11:59pm tonight, 20 January 2022, while the rest of New Zealand will remain at Orange as the Government prepares for Omicron to enter the community.
“Vaccination rates have continued to increase in Northland and are now at 89 percent first dose. The easing of the Auckland boundary over summer did not drive an increase in cases so we believe it is safe for Northland...
More>>

ALSO:


Gordon Campbell: On Responding To The Need In Tonga


The power of the Tonga eruption (and the size of the aid response being mounted) have been sobering indications of the scale of this disaster. The financial impact is certain to exceed the damage done by Cyclone Harold two years ago, which was estimated at the time to cost $US111 million via its effects on crops, housing and tourism facilities. This time, the tsunami damage, volcanic ash, sulphur dioxide contamination and villager relocation expenses are likely to cost considerably more to meet...
More>>



 
 



Science Media Centre: Omicron Outbreak Would Move The Country To Red - Expert Reaction

The Prime Minister has announced if Omicron cases spread into the community, the country will move to the traffic light system's Red setting within 48 hours. Jacinda Ardern also mentioned there will be changes to the country's testing regime, with more use of Rapid Antigen Tests... More>>


Government: New Zealand Prepared To Send Support To Tonga

New Zealand is ready to assist Tonga in its recovery from Saturday night’s undersea eruption and tsunami, Foreign Affairs Minister Nanaia Mahuta and Defence Minister Peeni Henare said today... More>>


Ministry of Health: COVID-19 Immunisation Starts For 5 To 11-year-old Tāmariki

More than 120,000 doses of the child (paediatric) Pfizer vaccine have been delivered to over 500 vaccination sites around New Zealand as health providers prepare to start immunising 5 to 11-year-olds tamariki from today, 17 January... More>>



Statistics: Departures Lift Border Crossing Numbers

The number of people crossing New Zealand’s border went up in November 2021, mostly due to an increase in departures, Stats NZ said today. There were 28,700 border crossings in November 2021, made up of 12,300 arrivals and 16,400 departures... More>>


Financial Services Federation: Open Letter To Government From Non-bank Lenders: The Path Forward On CCCFA Changes
Responsible lenders are not interested in telling the Government “I told you so” when it comes to unintended consequences of changes to lending laws that are now causing grief for everyday Kiwis seeking finance... More>>

CTU: Too Many Kiwi Workers Financially Vulnerable As Omicron Looms
With New Zealand on the precipice of an Omicron outbreak and the economic upheaval that comes with it, the CTU’s annual Mood of the Workforce Survey shows the vast majority of kiwi workers do not have the financial resources to survive a period of unemployment... More>>

 
 
 
 
 
 

LATEST HEADLINES

  • PARLIAMENT
  • POLITICS
  • REGIONAL
 
 

InfoPages News Channels