Staphylococcus aureus bacteria use an immune system trick to colonize up to 80% of humans, and that same strategy to evade vaccine-based immunity. This explains why all staph vaccines up to now have failed to provide clinically relevant immunity, according to a paper published last month in Cell Reports Medicine.

Research into vaccines for Staphylococcus aureus (S. aureus), the most common type of staph infection, has led to experimental vaccines that protect mice but fail in humans. A paper published Jan. 16 in Cell Reports Medicine explained why.

When a person first encounters staph, the bacterium fools the human immune system into releasing ineffective antibodies instead of the neutralizing antibodies typically associated with robust immunity. That “trick” allows S. aureus to colonize us, usually harmlessly.

When a colonized person’s immune system is later challenged with a staph vaccine it does not make new, effective antibodies. Instead, it calls up more of the same ineffective antibodies that allowed the bug to colonize the individual in the first place.