Risk Adjusted Non Pharmaceutical Interventions for the Management of COVID 19 in South Africa

A global analysis of the impact of non-pharmaceutical interventions (NPIs) on the dynamics of the spread of the COVID-19 indicates that these can be classified using the stringency index proposed by the Oxford COVID-19 Government Response Tracker(OxCGRT) team. The world average for the coefficient that linearises the level of transmission with respect to the OxCGRT stringency index is αs= 0.01±0.0017 (95%C.I.). The corresponding South African coefficient is αs= 0.0078±0.00036 (95%C.I.), compatible with the world average. Here, we implement the stringency index for the recently announced 5-tier regulatory alert system. Predictions are made for the spread of the virus for each alert level. Assuming constant rates of recovery and mortality, it is essential to increase αs. For the system to remain sub-critical, the rate with which αs increases should outpace that of the decrease of the stringency index. Monitoring of αs becomes essential to controlling the post-lockdown phase. Data from the Gauteng province obtained in May 2020 has been used to re-calibrate the model, where αs was found increase by 20% with respect to the period before lockdown. Predictions for the province are made in this light.