我们还可以确定的是，一旦大部分人群感染猪流感并获得免疫力，疾病的变种将会打破目前的免疫性并成为当下的压力。
We can also say that once most people have been infected by swine flu and become immune, a variant that can beat that immunity will replace the current strain.
这是因为再次接种时前次的免疫性仍然存在，抑或是因为在研究人群中再次接种率较低，对此目前尚无定论。
Whether this reflects the persistence of pre-existing immunity at the time of revaccination or lower rates of revaccination in the study populations cannot be determined.
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