But in a sign of Beijing’s continuing efforts to control the investigation, the team of scientists and W.H.O. employees almost immediately ran into obstacles. Two scientists were unable to enter China at the last minute and remained in Singapore because they tested positive for coronavirus antibodies, the W.H.O. said in a Twitter post. The Chinese authorities required the remaining 13 experts to undergo two weeks of quarantine in Wuhan, where the virus first emerged in late 2019.
A summer dip in UK coronavirus infections has pushed back test results for AstraZenca’s potential COVID-19 vaccine, leading the drugmaker to delay deliveries of shots to the UK government.