Don’t wait, re-escalate: delayed action results in longer duration of COVID-19 restrictions

Non-pharmaceutical public health interventions have significant economic and social costs, and minimizing their duration is paramont. Assuming that interventions are sufficient to reduce infection prevalence, we use a simple linear SIR model with case importation to determine the relationship between the timing of restrictions, duration of measures necessary to return the incidence to a set point, and the final size of the outbreak. The predictions of our linear SIR model agree well with COVID-19 data from Atlantic Canada, and are consistent with the predictions of more complex deterministic COVID-19 models. We conclude that earlier re-escalation of restrictions results in shorter disruptions, smaller outbreaks, and consequently, lower economic and social costs. Our key message is succinctly summarized as ‘don’t wait, re-escalate’ since delaying re-escalation of restrictions results in not only more infections, but also longer periods of restrictions.