Post-publication an investigation conducted by Elsevier's Research Integrity & Publishing Ethics team on behalf of the journal has found that ethical approval for the research presented in this paper was obtained retrospectively on 29 April 2020, after the data collection had already started. This was because the author's department did not have an ethics committee at the time. It should be noted that the authors submitted their study for review at the inaugural meeting of the ethics committee and received approval soon after.
A Sun, study studied this question.