There is still much to learn about Corona virus. One area that is particularly problematic is how to protect patients that are immunocompromised (roughly 5% of the US population) due to organ transplant, auto-immune/rheumatic diseases, cancer, and dialysis.
It has been long understood that the efficacy of many vaccines is attenuated in immunocompromised patients and this also seems to be the case for Covid-19 vaccines. Timing of the vaccine is important and it should be administered between chemotherapy cycles. For patients with stable rheumatology conditions suspending daily doses of mycophenolate and methotrexate for 1 to 2 weeks is advised.
A very small study has been done on administering a third dose of the m-RNA vaccine or administering the Johnson & Johnson vaccine to patients who already received two doses of an RNA vaccine. In the patients who had only very low antibody titers after their first two m-RNA vaccines, 100% developed excellent titers after a 3rd vaccine. However, in the patients with no detectable antibodies after their first two m-RNA vaccines, only 25% developed high antibody titers. Much larger study trials are underway to better address this issue. For the time being as America is unmasking, the previous guidelines for mask wearing and social isolation are still advised for immunocompromised patients.