If you have a large number of atoms in an aggregate, it is going to require that the substance turn solid and condense at room temperature.

如果有很多原子进行聚集，在室温下,会使的物质转变成固体状态。

麻省理工公开课 - 固态化学导论课程节选

So, it's more effective because it's a live virus but it's a little bit more concerning because it's a live virus as well, in that you trust that it's attenuated but could it convert back to a virulent form or a form that caused a disease.

因此,口服疫苗更加有效,因为它是活性病毒,但又是因为这一点,人们也存有更多顾虑,当它处于减毒状态时你会信任它,但是它会不会转变回,强毒壮态或者致病状态呢

耶鲁公开课 - 生物医学工程探索课程节选