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Abstract

The traditional long-term solutions for epidemic control involve eradication or population immunity. Here, we
analytically derive the existence of a third viable solution: a stable equilibrium at low case numbers, where
test-trace-and-isolate policies partially compensate for local spreading events and only moderate restrictions
remain necessary. In this equilibrium, daily cases stabilize around ten or fewer new infections per million people.
However, stability is endangered if restrictions are relaxed or case numbers grow too high. The latter destabilization
marks a tipping point beyond which the spread self-accelerates. We show that a lockdown can reestablish control
and that recurring lockdowns are not necessary given sustained, moderate contact reduction. We illustrate how
this strategy profits from vaccination and helps mitigate variants of concern. This strategy reduces cumulative
cases (and fatalities) four times more than strategies that only avoid hospital collapse. In the long term, immunization, large-scale testing, and international coordination will further facilitate control.