Low case numbers enable long-term stable pandemic control without lockdowns

TL;DR

This paper demonstrates that maintaining low case numbers through test-trace-isolate strategies can achieve long-term pandemic stability without lockdowns, especially when combined with vaccination and international coordination.

Contribution

It introduces a third stable equilibrium at low case numbers, supported by analytical derivation, showing how moderate restrictions and testing can sustain control without full lockdowns.

Findings

Stable equilibrium at around ten cases per million enables long-term control.

Relaxing restrictions beyond a threshold causes self-accelerating spread.

Vaccination and testing significantly reduce cumulative cases and fatalities.

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 new infections per million people or less. 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) 4x more than strategies that only avoid hospital collapse. In the long term, immunization, large-scale testing, and international coordination will further facilitate control.