We have published a new paper in the Journal of the Royal Society Interface on the effectiveness of manual and digital contact tracing for COVID-19. The study uses high-resolution SocioPatterns contact datasets from several contexts to evaluate the relative and combined impact of manual contact tracing (MCT) and digital app-based contact tracing.
The results show that the benefit (epidemic size reduction) is linear in the fraction of contacts recalled during MCT and quadratic in the app adoption rate, with no threshold effect. Benefits are higher and the cost lower when the epidemic reproductive number is lower, highlighting the importance of combining tracing with additional mitigation measures. The observed phenomenology is qualitatively robust across different datasets and parameters, and we obtain analytically similar results on simplified models.