Can contact tracing apps slow the spread of COVID-19?

"Outpatient Management of COVID-19: Rapid Evidence Review," in the current issue of AFP, discusses current testing and treatment recommendations. It includes quarantine recommendations for close contacts of COVID-19 individuals; to identify those contacts, the Centers for Disease Control and Prevention (CDC) recommends that public health departments conduct contact tracing for all confirmed COVID-19 positive persons. With infrastructure challenges limiting contract tracing in many parts of the US, contact tracing apps have been proposed as a possible solution, but they also bring several barriers to widespread implementation of their own.

The CDC advises that all close contacts of COVID-19 positive persons should be tested, and those who test negative should quarantine for 14 days. Robust contact tracing has the potential to dramatically decrease COVID-19 spread, and contact tracing apps promise to do what manual contact tracing has thus far struggled to keep up with:

[Y]our phone will regularly send out a beacon via Bluetooth that includes a random Bluetooth identifier — basically, a string of random numbers that aren’t tied to a user's identity and change every 10-20 minutes for additional protection...Other phones will be listening for these beacons and broadcasting theirs as well.....If you later come down with COVID-19, open the health app on your phone and log a diagnosis. The phone then uploads the last two weeks' worth of beacon data, and asks for your permission to anonymously share your results and notify others.

Similarly, if someone you have been in contact with reports a positive COVID-19 test, you can then be notified to get tested and begin quarantining. Concerns with privacy have affected uptake of these apps, and surveys suggest that many persons using them are unwilling to follow through on testing and quarantine recommendations. Of course, owning a smartphone is a prerequisite to using such an app as well; in the US, 19% of adults don't own a smartphone, and in adults over the age of 65, that percentage is 47%. 

Given these concerns, health leaders in Europe have raised concerns that contact tracing apps may be one part of the solution but cannot fully substitute for manual tracing efforts. Public health has been underfunded in the US for decades, despite data showing that most people find public health to be valuable; indeed, for every $1 spent in public health efforts in high-income countries, $14 in future health expenditures are saved. Perhaps the COVID-19 pandemic will provide the necessary momentum to improve our investment in these vital services.

In the meantime, you can continue to find current COVID-19 information and resources at the AFP By Topic: Coronavirus Disease 2019 site.