Blood for transfusion is screened principally using antibody tests. These tests can be negative for up to two months for an HIV-infected person and even longer

Blood for transfusion is screened principally using antibody tests. These tests can be negative for up to two months for an HIV-infected person and even longer in the case of Hep-C (retest at six months recommended to rule in/out). So, while the antibody tests used today have a very low false-negative rate, there remains a concern around people who may have contracted a blood-borne disease in the the last few months. As a gay man, I was for some time frustrated with donor exclusion policies related to MSM. However, keep in mind - blood donation is not any benefit to the donor, but rather to the recipient. It is in the best interest of the recipient for blood banks to obtain blood with the lowest risk of infection. For this reason, blood banks exclude a wide variety of donors with elevated risks of various infectious disease (MSM, IV drug user, in the UK in a certain time period, deployed overseas by military, etc depending on the organization). The number of people not excluded by these policies is normally sufficient to meet need, so it makes perfect sense for the blood banks to stick to a policy designed "out of an excess of caution" to avoid blood with higher risk of infectious disease. Because of improved accuracy and affordability of antibody testing, the exclusion period for MSM was reduced to 12 months (from lifetime). Because of an abnormal blood shortage related to COVID-19, FDA has temporarily reduced the exclusion for MSM and individuals with tattoos/piercings to 3 months. 3 months is actually cutting it somewhat close as far as reliable detection of antibodies, so the period will likely be increased again post-crisis to maintain a wide margin of safety. Organs are evaluated for suitability based on guidelines that are similar to, and often stricter than, blood donation.