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.
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。
2
Methods a retrospective investigation method was used to analysis the epidemic situation of pulmonary tuberculosis before and after BCG revaccination and prophylactic chemotherapy.
采取回顾性调查的方法，对BCG复种及预防性服药停止前后的肺结核疫情进行分析。
3
Therefore, the two indicators used as reflecting tuberculosis infection and onset after BCG revaccination termination were both not higher and even lower than the BCG revaccination group.