Nation Johnson & Johnson pauses COVID-19 vaccine trial due to unexplained illness — the second US trial now on hold October 12, 2020October 13, 2020Elizabeth Weise and Karen Weintraub, USA TODAYComments Off on Johnson & Johnson pauses COVID-19 vaccine trial due to unexplained illness — the second US trial now on hold The Phase 3 clinical trial was temporarily halted Monday because of an unexplained illness in one of the participants, Johnson & Johnson said.