Although not included in current vaccines, research shows that immunization with adenylate cyclase toxin elicits neutralizing antibodies. Neutralizing antibodies can block binding of the toxin to CR3.
The text describes a potential vaccine component: adenylate cyclase toxin.  It explains that while it's not currently used in vaccines, research shows that immunization with this toxin can generate antibodies that neutralize it and prevent its interaction with CR3.