Feedback mitigates the effect of waning compliance to health directives.

Left: After 50 days, the effectiveness of interventions decreases. Feedback control increases the level of interventions accordingly to stop pandemic growth. To fully counteract the (input) uncertainty, the cumulative error needs to be taken into account in the policy update (yellow; i.e., through the integrator term Ki). If not (purple), the pandemic is stabilized at a sustained higher level of infections. Right: This effect is amplified if only a limited number of intervention levels are available. The area under the curve not using the cumulative error (purple) is 85% higher than when the cumulative error is used (yellow).