When the Oxford University/AstraZeneca trials for a Covid-19 vaccine were paused last week, the team emphasised it was not uncommon in the testing of experimental vaccines. Little attention has been paid to such pauses and restarts in past trials but this time the news led to a 13 per cent fall in AstraZeneca stocks and prompted Chinese and Russian vaccine developers using similar technology to issue statements distancing themselves from the collaborative candidate. After four days, British regulators gave the green light for trials to resume, saying it was expected that some would become unwell in large-scale trials. No information about the patient was disclosed, to preserve confidentiality, but the person reportedly developed symptoms of a rare spinal inflammation. Oxford restarts trial of AstraZeneca Covid-19 vaccine after pause The prompt resumption suggested the regulators were convinced the condition was not related to the vaccine and that the person had recovered. Scientists argued the pause showed the team was following safety guidelines, but some said the safety bar would inevitably be raised afterwards and there would be more concerns about the US regulator’s consideration to give emergency use authorisation (EUA) to some candidates before trials were completed. China did well in publishing data from the first two stages of trials in international journals. But many were shocked to learn last month that hundreds of thousands had been inoculated with experimental vaccines under an EUA granted by Chinese authorities in late July. China already using Covid-19 vaccine candidate on key workers, official says A justification for the EUA was that high risk groups could not wait for trials to be completed, but the numbers revealed to have been vaccinated in China has cast doubt on whether they all were necessary. The process was kept under wraps for more than a month before it was officially disclosed and some recipients reportedly signed confidentiality agreements about the inoculations. Zhou Song, a senior official with the China National Biotec Group, parent of Sinopharm, developer of two Covid-19 vaccine candidates, said last week there had been no cases of infection among the participants , many of whom had travelled abroad since receiving the jab. China intended to send a message that its vaccines are safe but the late disclosures and large-scale vaccinations outside formal trials could be counterproductive in its bid to win international confidence in a Chinese vaccine. One remedy would be the more timely release of detailed data about EUAs.