Modelling the effect of an improved trace and isolate system in the wake of a highly transmissible Covid-19 variant with potential vaccine escape

Objective How helpful would a properly functioning find, test, trace, isolate and support (FTTIS) system be now in the UK with new Covid-19 infections at a low level and half the adult population immunised but with a highly transmissible variant becoming predominant? Design a dynamic causal model of Covid-19 supplied with the latest available empirical data is used to assess the impact of a new highly transmissible variant. Setting the United Kingdom. Participants a population based study. Interventions scenarios are used to explore a Covid-19 transmission rate 50% more and twice the current rate with or without a more effective FTTIS system. Main outcome measures incidence, death rate and reproductive ratio Results a small short third wave of infections occurs which does not occur if FTTIS effectiveness is improved from 25% to 30%. Conclusion a modest improvement in FTTIS would prevent a third wave caused by a highly transmissible virus.