Source: South China Morning PostWhen 26-year-old Peter Zhou graduated from medical school in New York and wished to return to Shanghai last month, he was faced with a dilemma: the antibody protection he received from a Covid-19 vaccine jab might be the very reason he could not go home.In November, China started to insist inbound passengers produce evidence of testing negative for the antibody immunoglobulin M (IgM) – usually the first type of antibody produced against virus infection – along with a negative Covid-19 test…Read More