Question

dimitri received a flu vaccination earlier in the year. however, he has just been tested and has a confirmed case of the flu. why did dimitri most likely get the flu? vaccinations are not always effective. vaccinations are not effective if hygiene is poor. vaccinations give individuals the flu with full symptoms. vaccinations work only when provided at the onset of the disease.

Explanation:

疫苗并非总是100%有效。即使接种了流感疫苗，个体仍有可能感染流感。卫生条件差不是接种疫苗后仍感染流感的主要原因；疫苗不会让个体出现完整的流感症状；疫苗也不是仅在疾病发作时才起作用。

Answer:

Vaccinations are not always effective.