non-responder           
noun [ C ]  specialized (also nonresponder) uk/ˌnɒn.rɪˈspɒn.dər/ us/ˌnɑːn.rɪˈspɑːn.dɚ/
 social science 未回答者;未答复者;未应答者
a person who does not answer a request for information
  Sixty of the people we surveyed were non-responders. 在我们调查的人中,有60人没有回应。 
 We sent out a reminder to all the non-responders. 我们向所有未回复调查者发了提醒。 
 Synonym: non-respondent
  medicine (治疗)无反应者
an ill person who does not begin to get better when they are given treatment
  She is a nonresponder to aspirin.
 If the patient is a non-responder, the therapy should be stopped. 如果病人没有反应,应该停止治疗。 
 - More examples
 - We approached the non-responders two years later for interviews.
 - When we performed an analysis of responders and non-responders, there were no significant differences between them.
 - The manufacturer will pay back half of the cost for each non-responder.