The vaccine in this instance is all about delivering a target to the immune system's sentries. If those sentries are defective, or if the hitmen the sentries ne

The vaccine in this instance is all about delivering a target to the immune system's sentries. If those sentries are defective, or if the hitmen the sentries need to alert are defective, there's nothing this vaccine can do to change that. "Immune compromise" is generally used as a blanket term, but in many people there are specific immune deficiencies, which may or may not factor into the pathway being targeted here. For instance, natalizumab screws with immune cells' translocation across membranes, and shouldn't play a role in responding to a vaccine (I mean, if it wasn't off the market anyway). If it's a general immune dysfunction (cancer, diabetes), they will see some benefit, but it will be much reduced - specifically because both responding to the vaccine, and responding to the virus post-vaccination, require the activity of the immune system. What this means precisely will vary with the degree and nature of the immune dysfunction: some folks might see some antibody response, and benefit from repeat dosing. Others might fail to seroconvert altogether, in which case it is what it is.