In a previous study focused on HBV vaccination among people living with HIV/AIDS, it found that anti-HBe titers in a low CD4+ group were much lower than a high CD4+ group (low CD4+ group: 462 mIU/ml vs high CD4+ group: 8834 mIU/ml), which shows that an immunosuppressed state can affect the ability to produce protective anti-HBe [27]. Here, CD4 is linked to AIDS.