Yang Wen-kuang explains that since everyone has at some time been infected by and developed immunity against such viruses, their use in small quantities is ineffective for delivery of the required genes. On the other hand, if too much of the virus is used, this may bring on an acute reaction such as asthma.
楊文光指出，由於每個人都感染過腺病毒，體內都有免疫力，用量少無法達到基因傳送的目的；用多了又會產生嚴重類似哮喘的急性反應。