The OP has seriously overposted over the same issue.
People who have no immunity, being those who are:
1) on anti-rejection meds post an organ transplant;
2) on aggressive chemotherapy;
3) at terminal, end stage of cancer.
What contributes the rare people who produce antibodies beyond 3months and reach 6months.thanks
CDC, FDA and manufacture of the tests say 3 months. 6 months is outdated.