Failure of the blocking drug is also undetectable during the window period. Even if the blocking drug fails and the virus is already infected in the body, it is still undetectable during the window period, because the window period is the period of time during which the virus is already infected but the labs are still negative, which may last up to three months. So clinically, after taking oral blocking drugs, you still need to do regular laboratory tests. For example, once a month, three months, or even six months, depending on the virus, the window period is different. If there is a high risk of exposure to infectious diseases, it is recommended that regular blockade be conducted under the guidance of an infectious disease physician, so as to improve the efficiency of blockade, while regularly testing indicators.