@bid compliance may have been one issue affecting the results...

@bid compliance may have been one issue affecting the results but one observation that stuck in my mind was that the test results were based on tests on day 7 only.

I read a theory, l think somewhere in HC, that the younger participants more than likely had recovered by day 7 as younger people generally do from the common cold or flu therefore the results on that basis alone showed no statistical significance.

This means the trial may have shown different more favourable results if testing was conducted on day 5 or 6 for example.

Given this theory, which to me sounds very feasible, then you could say the trial design was flawed perhaps causing a lost golden opportunity.

Any comments welcome.