Drug-maker AstraZeneca has temporarily suspended its COVID-19 vaccine tests after an “unexplained illness” in a person who took the treatment. In a statement released Tuesday, the company said, “This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials.” The announcement came shortly after the drug-maker joined eight other companies in a promise to follow safety measures in vaccine development. AstraZeneca’s vaccine candidate is being developed with the University of Oxford. It has been described by the World Health Organization (WHO) as probably the world’s leading vaccine candidate to fight COVID-19. On Wednesday, Dr. Soumya Swaminathan, the WHO’s chief scientist, said “for drugs and vaccines which are given to people, you have to test their safety, first and foremost.”