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A mock up of a COVID-19 coronavirus vaccine. SARS-COV2, 2019-nCoV or COVID-19 is a contagious virus that causes respiratory infection. The World Health Organization is tracking 196 vaccine studies as of October 2020. Of these, 42 are undergoing clinical trials on humans, and eight are in phase three: large-scale trials to test their effectiveness. AstraZeneca and the University of Oxford have developed a vaccine based on a virus taken from chimpanzees, but the trial stopped for a week after one volunteer fell ill – it is continuing in the UK but not the US. Another, Novavax, is launching a larger phase three trial after a study of 10,000 volunteers in the UK. In the US Johnson & Johnson meanwhile halted vaccine trials after a subject became ill.China and Russia have already approved some vaccines for limited use. (KEYSTONE/CAMERA PRESS/Rob Welham)