主题：【求助】乙肝两对半2阳性5弱阳性的困惑 -- 火三木四

Your example about 外祖母大三阳 proved exactly that 日常接触传染乙肝, otherwise, the situation that 儿子有免疫力 would not occur. Yes, adults with normal immune system would recover from HBV infection, but nobody can be sure his/her immune system always work robustly. Besides, young children may become HBV carriers when infected.

10% carrier rate in Asian countries (China, Korea, Japan, Vietnam) cannot be explained by mother-children vertical transmission. HBV rate is significantly lower in western countries long before the introduction of HBV vaccine, or the sharing of syringes in vaccination. The sanitation condition, personal hygiene and dinning habits must have contributed significantly to the widespread of HBV.

By the way, 肝功能全正常 <>肝全正常.