Vaccines26 Nov 2020 20:53
vaccine makers tightly controlled who was enrolled to their trials, their vaccine dosages, the timing of those doses and much more - but they did not monitor participants' other behaviors, like mask-wearing, that affect infection risks.
Trial participants were left to decide for themselves where and how often to wear masks and how to practice social distancing, one told Business Insider.
And these differences in how coronavirus vaccine trial participants behaved could have drastic effects on how likely people who got the vaccine, versus those who got a placebo, were to get infected.
Neither Moderna nor Pfizer gave trial participants instructions on how to behave to try to reduce their infection risks (or not), and didn't log ths behaviors either, unless they suspected someone had caught coronavirus.
It doesn't necessarily mean that the two leading vaccines don't live up to the 90 percent efficacy found by their trials, but it does leave a gap in what we know about how much protection is offered by a shot versus by masking and social distancing.
And it comes as the results of AstraZeneca's trial for the Oxford University-designed shot come under fire after Oxford acknowledged that it was a manufacturing error that led it to try giving participants a half-dose for their first shot - an accidental arm of the trial that proved most effective.