一个英国教授的回答是 A negative Elisa test at 8 weeks can be considered conclusive in practical terms as the vast majority of people would have seroconverted by then. However current guidelines would only consider it conclusive after 12 weeks.
就是对于一线工作者来说,在实践操作中认为8周已经是足够安全的了;但是官方规定的指导是12周;然后他后面还说了让对方12周再去测下,但是他十分肯定结果会是阴。