The first coronavirus vaccine that aims to protect people with a single shot has entered the final stages of testing in the United States in an international trial that will recruit up to 60,000 participants.





The experimental vaccine being developed by pharmaceutical giant Johnson & Johnson is the fourth vaccine to enter the large, Phase 3 trials in the United States that will determine whether they are effective and safe. Paul Stoffels, chief scientific officer of J&J, predicted that there may be enough data to have results by the end of the year and said the company plans to manufacture 1 billion doses next year.





Three other vaccine candidates have a head start, with U.S. trials that began earlier in the summer, but the vaccine being developed by Janssen Pharmaceutical Companies, a division of J&J, has several advantages that could make it logistically easier to administer and distribute if it is proved safe and effective.





The company is initially testing a single dose, whereas the other vaccines being tested in the United States require a return visit and second shot three to four weeks after the first one to trigger a protective immune response. The J&J vaccine can also be stored in liquid form at refrigerator temperatures for three months, whereas two of the front-runner candidates must be frozen or kept at ultracold temperatures for long-term storage.