The modelled impact of MSM deferral policies on blood safety

28/04/26

In 2015 and 2022, CEBaP conducted systematic reviews on the safety of blood donation by men who have sex with men (MSM). At that time, the evidence supporting shorter or removed deferral periods was limited. Several countries have relaxed their MSM deferral policies, largely based on modelling studies, as experimental research in this area raises ethical concerns. These modelling studies were not included in the previous systematic reviews conducted by CEBaP. 

We performed a systematic review of modelling studies evaluating the impact of easing MSM deferral rules on blood safety. Fourteen models from five Western countries (France, the United Kingdom, the USA, Canada, and Israel) were identified, all focusing on HIV risk. The models suggest that relaxing deferrals results in only a very small increase in HIV transmission risk through transfusion. Although relative risk may increase up to three-fold, the absolute impact is minimal, with fewer than one additional HIV-positive unit per million donations. Overall risk therefore remains very low. Relaxed policies were also estimated to increase the donor pool by 0.04% to 2.1%.

None of the models assessed the impact on other transfusion-transmissible infections such as syphilis or hepatitis C.

In conclusion, while easing MSM donor criteria slightly increases HIV risk, the absolute risk remains very low and differences between policy options are small. Future models should also consider infections beyond HIV.

Read the full review published in Bulletin of the World Health Organization here.