Reintroduction of measures from Da Nang to Auckland is a reminder that once venues reopened/restrictions lifted, cannot assume contact tracing alone will be sufficient to control local transmission (consistent with modelling analysis: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30457-6/fulltext) 1/

Coverage often focuses on test & trace as if it were a single solution, but it’s one tool of several. Outbreaks globally (e.g. South Korea, Vietnam, Singapore, Hong Kong) show that other measures (restrictions on gatherings, remote working, venue closures) needed alongside. 2/

TTI works better with low case numbers & social distancing, because as outbreaks grow, it's harder to trace all contacts, and % of transmission that TTI can prevent shrinks. As @mlipsitch puts it, “you don't clean up an oil spill with paper towels” https://www.nytimes.com/reuters/2020/08/04/world/europe/04reuters-health-coronavirus-tracing-specialreport.html 3/

We need to find ways to reduce risk & reduce disruption of measures, but shouldn't expect one measure to do all the work. TTI approach has also been different in Asia, so won't necessarily see same results if implemented differently elsewhere: https://twitter.com/AdamJKucharski/status/1256140519572484102?s=20 4/4