Fascinating. There are two fascinating claims here that seem reasonably persuasive:
Economics and public health are meeting in increasingly interesting ways.
1. Hepatitis B infection biases live births to male infants. (Hep B infection is very common in some areas of China and used to be very common in Taiwan -- until they began immunizing newborns to prevent perinatal infection.)
2. This phenomena accounts for a significant portion of China's gender bias (too few women -- the other explanations are selective neglect of liveborn girls and selective abortion, the old explanation of 'stopping after the first boy' doesn't work).