这一时期被称为“空窗期”，如果献血在这期间进行，那么就存在较小的残留风险可能会传播病毒。
This period is referred to as the "window period," and if a donation is made during this time there remains a very small residual risk of viral transmission.
出现了新的对策，它们可以有效地降低以前残留的风险。
New countermeasures become available that can effectively mitigate risks previously categorized as residual.
有一点很重要：如果发现对策不是经济有效的，那么仍然会残留一些风险，无法降低这些风险。
This next point is important: If a countermeasure is found not to be cost-effective, the residual risks remain and these risks cannot be mitigated.
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