The details are what we'd need to know what "effective" means. Is it 7% effective? 37%? 97% I know you know that, of course. So many numbers and stats are being thrown around these days, and as lawyers and statisticians know, statistics can be made to show much of whatever you want them to show if you know how to manipulate them effectively.
As the old joke goes, "50% of the time it works 100% of the time."