Border workers should be tested every 4 days to beat delta, modelling suggests

Embargoed until: Publicly released: 2021-09-28 09:01

New Zealand

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New Zealand researchers have used a model to measure how vaccinating the border workforce of a country changes the risk of the virus spreading in a largely-unvaccinated population. They say while vaccines are highly effective in preventing disease, their effectiveness in preventing infection and transmission of the virus is less certain, so there's a danger that vaccination could prevent symptoms but not transmission. The researchers estimate that if a vaccine reduces transmission by 50%, vaccination of border workers increases the risk of a major outbreak from around 7% per initial case to around 9% per initial case. However, they say this increased risk can be reduced by routinely testing workers every four days.

Media release

From: The Royal Society

New Zealand and Australia have followed a COVID-19 elimination strategy, focusing on strict border controls to keep the virus out of the community. One point of weakness in this strategy is the large workforce involved in running government-managed quarantine facilities. These workers are at high risk of exposure to the virus and this has resulted in border incursions in both countries. This has led to frontline workers being prioritised for vaccination. Here we use a model to investigate the effect that priority vaccination of the border workforce has on the risk of outbreaks in an unvaccinated population. We find that, if the vaccine is effective in preventing symptoms but less effective in reducing transmission of the virus, the risk of community outbreaks can increase because it is more difficult to find asymptomatic cases in the border workforce. This risk can be effectively mitigated by regular routine testing of frontline workers.

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Journal/
conference: Royal Society Open Science

Research:Paper

Organisation/s: University of Canterbury, University of Auckland, Te Pūnaha Matatini

Funder: This work was funded by the New Zealand Ministry of Business, Innovation and Employment and Te Pūnaha Matatini and Centre of Research Excellence in Complex Systems.

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