Ann: Phase III prophylaxis trial for CS-8958 , page-29

My understanding of the possbile reasions is : The efficacy is measured by "risk reduction rate". The "risk reduction rate" is comparative and depends on the results of both the groups taking CS-8958 and placebo. The results of the group taking placebo can not be influenced by Inavir, but can be influenced by other such factors as using masks and other preventive measures. The result of the group taking CS-8958 can be influenced by both Inavir and the above mentioned other factors. The "risk reduction rate" is derived by comparing the results of the two groups. As we know, the 2009 pandemic was not as severe as it was initially expected (the placebo group had only 8.6% infection rate according to the ann), so the "risk reductio rate" does not sufficiently reflect the true efficacy of Inavir.That is, the infection rate is not large enough for a reliable result.


Just my thoughts.