White House pressure for a vaccine raises risk the U.S. will approve one that doesn’t work

“'If you give an emergency use authorization, you’re likely going to make it hard to assess all these vaccines and to assess the thing we really care about: Are they effective in preventing infection? That’s the key...'

The fastest vaccine ever developed, for mumps, took four years. Many experimental vaccines show promise in early human trials, which look at a shot’s safety and whether it prompts an immune response, but a significant chunk go on to flunk the broad final study of effectiveness known as a phase three trial. Patients may produce antibodies in response to a dose of an experimental vaccine, but those are not always strong enough to protect against a disease."

https://www.politico.com/news/2020/06/15/pressure-coronavirus-vaccine-risk-approval-316094