The infection mortality rate ( IFR ) incorporates a further adjustment to allow for undiagnosed and/or asymptomatic infections ; Oxford 's Centre for Evidence-Based Medicine has estimated a global IFR of 0.29 % as of 22 March 2020.Over time , estimates for the CFR in China decreased from 17.3 % ( for those with symptom onset 1–10 January 2020 ) to 0.7 % ( for those with symptom onset after 1 February 2020 ) .
A worldwide IFR of less than 0.25 % has been estimated by Oxford 's Centre for Evidence-Based Medicine .