灭活疫苗有效率50%意义是完全无症状的可能性大50%。总体的实际效果似乎和Pfizer差不多。要看具体测定过程，

来源: huntridge 于 2021-01-13 19:10:54 [档案] [博客] [旧帖] [给我悄悄话] 本文已被阅读：次 (7488 bytes)

巴西的有效率数据的分类：

https://www.toutiao.com/a6917212628884587019/?

那为何巴西的有效率数据最低？与巴西的统计方法有关。据相关媒体报道，在巴西的临床试验中，感染者都被分成了6类：无症状者、非常轻微症状者、轻微症状者、1级中度症状者，2级中度症状者，严重症状者。

具体来看，50.38%的有效率，只包含后面的5类症状；包含后4类症状，有效率便可达78%；若只比较严重症状者，则有效率可达100%。

Pfizer等的protocol是症状结合PCR test：

https://www.bmj.com/content/bmj/371/bmj.m4058.full.pdf

但是Peter Doshi提出质疑。需要更多细节和原始数据：

https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-modernas-95-effective-vaccines-we-need-more-details-and-the-raw-data/

“Suspected covid-19”

All attention has focused on the dramatic efficacy results: Pfizer reported 170 PCR confirmed covid-19 cases, split 8 to 162 between vaccine and placebo groups. But these numbers were dwarfed by a category of disease called “suspected covid-19”—those with symptomatic covid-19 that were not PCR confirmed. According to FDA’s report on Pfizer’s vaccine, there were “3410 total cases of suspected, but unconfirmed covid-19 in the overall study population, 1594 occurred in the vaccine group vs. 1816 in the placebo group.”

打疫苗的有疑似症状的远多于没有打疫苗的。Doshi质疑的要点是PCR测试假阴性。所以要求更多细节和原始数据。在没有这些数据之前，总体的实际效果似乎和Pfizer差不多。