As I prepared to get my shot in mid-December as part of a covid vaccine trial run by Janssen Pharmaceuticals, I considered the escape routes. Bailing out of the trial was a very real consideration since two other vaccines, made by Moderna and Pfizer-BioNTech, had been deemed safe and effective for emergency approval.
Leaving the trial would be a perfectly sane decision for me or anyone who had volunteered for an ongoing covid experiment. Why risk getting covid-19 if I was given a placebo, a shot with no vaccine in it? The way tests are designed, I might not be told whether I received the vaccine until the clinical trial is over, months from now.
Dropping the placebo arm could also be ethically sound from the company’s point of view. Researchers frequently halt trials when they have a product that works — or manifestly doesn’t. And the two approved vaccines are 95% effective.