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 will be shipped frozen, but can 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 until shortly before use.
“A single-shot vaccine, if it’s safe and effective, will have substantial logistic advantages for global pandemic control,” said [the Beth Israel Deaconess Medical Center’s] Dan Barouch.















