關鍵在於

滅活疫苗的免疫原性不夠強，在老年人誘導不出足以抗衡新冠病毒的抗體。

 

俺以前寫的 https://bbs.wenxuecity.com/health/946237.html

 

 

參見

https://www.nature.com/articles/s41577-020-00434-6

killed virus vaccines sometimes require the inclusion of an adjuvant and repeated administration for full efficacy