Mobile app to estimate COVID-19 transmission risk feasible, acceptable among users

A web-based mobile application (app) called MyCOVIDRisk estimates the risk of COVID-19 transmission and has been found to be feasible and acceptable among the US public, a study has shown. Transmission risk can be estimated for app users, without collecting personal health data, based on local prevalence of disease, type of activity, and mitigation measures employed.

“MyCOVIDRisk could serve as a model of mobile apps that enhance public awareness and gamify risk mitigation,” the developers said. “Although the impact of the app on COVID-19 fatigue and anxiety has not yet been elucidated, apps such as MyCOVIDRisk may help the public make more nuanced decisions that allow safe activities to continue when pandemics last for months.”

The MyCOVIDRisk app was conceived in July 2020. The developers reviewed published studies on transmission dynamics and protective measures, COVID-19 risk scores, and risk assessment apps or websites and sought to identify infection risk factors, sources of reliable prevalence data, attack rates associated with different activities, and studies modeling the effect of mitigation factors.

Four steps were undertaken to identify a simple model that would predict infection risk and make the development process shorter and less complicated: data understanding, model assembly, model and audit, and model delivery. [BMJ Innovations 2021;7:363-367]

“Consistent with best practices for digital health behaviour change, we provided personalization and interactivity, used multiple techniques for engagement, and included both positive and negative feedback,” the developers said. “We worked with a [user experience] expert to design icons that were visually appealing and inclusive.”

Based on the initial review, the following risk factors were included: location near high COVID-19 prevalence counties, indoor activities, poor ventilation, long duration of visits, physical exertion, and close proximity to others. [medRxiv 2020;doi:10.1101/2020.02.28.20029272; Clin Infect Dis 2021;72:604-610]

Mitigations factors were as follows: wearing a mask, distancing, reducing activity time, washing hands, increasing ventilation, and wearing eye protection. [Wellcome Open Res 2020;5:98; Lancet 2020;395:1973-1987; ACS Nano 2020;14:6339-6347; https://www.descarteslabs.com/resources/covid-19-now; https://www.livescience.com/face-masks-eye-protection-covid-19-prevention.html]

In consideration of iterative user feedback on the initial app wireframe, the developers reordered screens, redesigned input icons, changed input screens for activity time and percent of people masked, included checkboxes to ensure its use in the US, and moved detailed modeling information to optional screens.

The MyCOVIDRisk app was launched on 1 October 2020. Over 1 million users in 112 countries (96.5 percent in the US) have accessed the app as of 18 December 2020. The most common activity selected was meeting at friend’s house (22.6 percent of respondents), followed by shopping (20.2 percent) and taking a walk (11.6 percent).

Among those using mitigation steps, nearly all (99.9 percent) selected social distancing and majority (83.7 percent) planned to wear a mask.

“Future work should include considerations of how to disseminate and motivate use of the app by those who may be sceptical or unaware, and how to enhance use of mitigation steps,” the developers said. “Additional modifications could include enhancement of more complex risk modelling (eg, travel, doctor’s visits), ‘behavioural nudges,’ or linkages to testing.”