PM Jacinda Ardern reveals how Kiwis will be able to book their Covid vaccinations through a nationwide system ahead of mass rollout.

Contact tracing can reduce the spread of Covid-19 by up to 60% – but the most critical factor in curbing an outbreak remains how well people isolate themselves quickly.

That’s according to new modeling that comes at a time when experts warn New Zealand is more vulnerable than ever to another big push.

In their study, University of Canterbury Associate Professor of Mathematics Alex James and his colleagues at Te Punaha Matatini developed a smart model that quantified, for the first time, how much of a difference contact tracing can make against an epidemic.

This included modeling how many contacts could be traced, how long it took to reach them and tell them to self-isolate, and how effective that self-isolation ultimately turned out to be.

While data provided by New Zealand’s contact tracing system helped with their estimates, the researchers were still able to test several other values ​​to find out which variables were most important.

Their analysis suggested that, as part of bringing the country’s national outbreak under control in April last year, the testing and tracing system reduced the spread rate from 35 to 45 percent.

And because the system had improved since then, they found that contact tracing reduced transmission by more than that when responding to the Auckland August cluster.

Overall, modeling indicated that a fast, high-quality contact tracing system, combined with strong support for people in quarantine or isolation, could reduce the rate of spread by up to 60%.

But if cases weren’t isolated and contacts weren’t quarantined as easily, or if some contacts weren’t traced, or traced more slowly, that impact dropped to around 40%.

Interestingly, they also found that the best measure of a contact tracing system’s performance was not the proportion of cases detected before they became symptomatic, but the time between quarantining a person. infected and quarantining their contacts.

If at least 80% of cases were quarantined or isolated within four days of quarantining or isolating the source or “index” case, for example, the rate of spread could be reduced by at least 40% .

The researchers noted how epidemiologist Dr Ayesha Verrall identified this as a key criterion in his urgent and influential audit of New Zealand’s system last year, before later becoming Associate Minister of Health.


“We have shown that while the effectiveness of quarantine and isolation can be guaranteed, this criterion can be useful in comparing a system,” the researchers said.

They also reported that the speed and capacity of contact tracing systems were likely to be more cost effective than enforcing social distancing measures, although these might also be necessary.

“The critical importance of effective quarantine and isolation makes essential the existence of a universal social security benefit such as rights to paid leave for pre-symptomatic or asymptomatic people in quarantine, and security of ‘adequate employment and unemployment benefits,’ they concluded.

Likewise, the need to quickly trace the majority of contacts means that it is essential to invest in qualified professionals and workers trained in public health work.

“The experience of the contact tracing effort in New Zealand shows that the development of trusting relationships by public health officials is essential to an effective system.”

Study co-author Professor Michael Plank added that with the nationwide rollout of the vaccine still in its infancy and highly infectious variants dominant globally, New Zealand remained more vulnerable to Covid- 19 than ever.

“So it is very important that you continue to use the app and for anyone who is even slightly ill to stay home and get tested.”

A spokesperson for the Department of Health said New Zealand has been using the performance indicators suggested in the study since August last year.

The study comes as experts have called for improvements to the country’s system since a review of the August outbreak found the number of cases that can be traced was well below the promised 1,000 per day.

Before the outbreak hit, it was believed that contacts of 1,000 cases could be traced per day, with the Auckland Regional Public Health ARPH due to trace 120.

But the cluster was much more complex than the first outbreak in April as it largely affected the Pacific community who interacted closely with their community.

While the two experts who conducted a review of the response – Sir Brian Roche and Professor Philip Hill – found that the test and tracing system ultimately provided a timely and informed effort, they nevertheless suggested that its ability and its financial stability needed to be “urgently rectified” within two to three years.

Since then, however, the ministry spokesman said the capacity of the system had been “significantly increased”.

During the outbreaks of January and February, the Ministry’s National Investigation and Research Center (NITC) and public health units were able to manage cases and contacts without calling on the workforce. supplement ”larger, which had several thousand employees.

In addition to improving technology and operational procedures, NITC was now able to track more than 40,000 travelers, as part of non-quarantine travel zones tracking.

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This notice was published: 2021-06-17 04:52:41


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