Clinical trial results from an experimental coronavirus vaccine AstraZeneca (NYSE: AZN) licensed from Oxford University might not be ready this September as hoped. In an interview with The Telegraph, the director of Oxford's Jenner Institute, Professor Adrian Hill, said the chances we'll see meaningful trial results by September are increasingly slim due to successful COVID-19 containment efforts. Vaccine math is hard In April, Prof. Hill said a million doses could be ready by September if results from ongoing efficacy tests prove ChAdOx1 nCoV-19 is safe and effective. Thanks to successful containment efforts, Hill thinks the number of new infections in the U.K. will be too few to draw any meaningful conclusions at such an early date. Out of around 10,000 people expected to enroll in the trial, the researcher expects less than 50 will catch the virus. Image source: Getty Images. While AstraZeneca can easily solve this problem by expanding the study, we still need to wait and see if new participants injected with the vaccine come down with COVID-19 less often than those randomized to receive a placebo. It's not unusual to see COVID-19 infections put healthy, athletic people in the hospital or worse. Despite popular suggestions, willingly exposing trial participants to SARS-CoV-2 to speed up the vaccine development process is unethical and illegal in at least a hundred different ways. Recently, AstraZeneca signed an agreement to provide up to 300 million doses of ChAdOx1 nCoV-19 to the U.S. if it works as intended. The company could receive up to $1.2 billion to assist with the vaccine candidate's development, including a clinical trial expected to enroll 30,000 participants. 10 stocks we like better than AstraZenecaWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and AstraZeneca wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of April 16, 2020 Cory Renauer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source