> Odds are it does make things more effective rather than less, based on our experience with other vaccines. But IMO it's not wise, because it wasn't studied.
It has since been studied[1] (preprint) and that was exactly what was found -- delaying the second dose provoked a stronger response, similar to many other vaccines.
Sure, so far preliminary data looks OK. I still don't think it was a wonderful roll of the dice-- it didn't lower susceptibility so much in the short term (because a single dose's efficacy is limited, especially in the old) and it could have made things much worse.
It has since been studied[1] (preprint) and that was exactly what was found -- delaying the second dose provoked a stronger response, similar to many other vaccines.
[1] https://www.birmingham.ac.uk/news/latest/2021/05/covid-pfize...