Contact-Tracing Apps could Improve Vaccination Strategies

Mathematical modeling of disease spread suggests that herd immunity could be achieved with fewer vaccine doses using Bluetooth-based contact-tracing apps to identify people who have more exposure to others – and targeting them for vaccinationMark Penney, Yigit Yargic and their colleagues from the Perimeter Institute for Theoretical Physics in Ontario, Canada, present this approach in the open-access journal PLOS ONE on September 22, 2021.
The COVID-19 pandemic has raised questions about how to best allocate limited supplies of vaccines for the greatest benefit against a diseaseMathematical models suggest that vaccines like those available for COVID-19 are most effective at reducing transmission when they are targeted to people who have more exposure to othersHowever, it can be challenging to identify such individuals.

Penney and colleagues hypothesized that this challenge could be addressed harnessing existing apps that anonymously alert users to potential COVID-19 exposureThese apps use Bluetooth technology to determine the duration of contact between any pair of individuals who both have the same app downloaded on their smart phonesThe researchers wondered whether this technology could also be used to help identify and target vaccines to those with greater exposure – a strategy analogous to a wildfire-fighting practice called “hot-spotting,” which targets sites with intense fires.

To explore the effectiveness of a hot-spotting approach to vaccination, Penney and colleagues used mathematical modeling to simulate how a disease would spread among a population with such a strategy in placeSpecifically, they applied an analytical technique borrowed from statistical physics known as percolation theory.

The findings suggest that a Bluetooth-based hot-spotting approach to vaccination could reduce the number of vaccine doses needed to achieve herd immunity up to one halfThe researchers found improvements even for simulations in which relatively few people use contact-tracing apps – a situation mirroring reality for COVID-19 in many regions.

In the future, the modeling approach used for this study could be refined, such as incorporating the effects of strains on the healthcare systemNonetheless, the researchers note, the new findings highlight a technically feasible way to implement a strategy that previous research already supports.

The authors add: “The technology underlying digital contact tracing apps has made it possible to implement novel decentralized and efficient vaccine strategies.”

Mark D Penney, Yigit Yargic, Lee Smolin, Edward W Thommes, Madhur Anand, Chris T Bauch.
“Hot-spotting” to improve vaccine allocation harnessing digital contact tracing technology: An application of percolation theory.
PLOS ONE, 2021doi: 10.1371/journal.pone.0256889

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