Effect of Alert Level 4 on Reff : review of international COVID-19 cases

This study mapped the coronavirus epidemic curve for 25 countries and modeled how the spread of the virus has changed in response to the various lockdown measures. It classifies each country’s public health response using New Zealand’s four alert system. Levels 1 and 2 represent relatively relaxed controls, whereas levels 3 and 4 are stricter. By mapping the change in the effective reproduction number (Reff, an indicator of the actual spread of the virus in the community) against response measures, the research shows countries that implemented level 3 and 4 restrictions sooner had greater success in pushing Reff to below 1.