I am confused here?

I am confused here,  why I am "而且有可能你已经是隐性病毒携带者（华人中比例极高）"?

I did have vaccine long time ago, about ten years ago. Now just wondering whether I should get vaccine to boost the antibody? why I am 隐性病毒携带者? Really confused, could you explain more? this is really scary!