That is right. We don’t know what mutations might make the virus attenuated (mild), but we can use what Nature has done to tell us. We also get human data on sa

That is right. We don’t know what mutations might make the virus attenuated (mild), but we can use what Nature has done to tell us. We also get human data on safety thrown in for free. This makes a huge difference in how quickly we can use a new strain in people even under controlled conditions.