HMM: A chain reaction: HIV vaccines can lead to antibodies against antibodies. “When they carried out the experiments on blood from animals that had received multiple doses of an experimental HIV vaccine, they discovered something surprising: some of the antibodies were not binding directly to the HIV viral antigen, but to immune molecules on its surface. . . . In a series of follow-up experiments on HIV-vaccinated animals, Brown, Ward, and their colleagues showed that these kinds of anti-immune complex antibodies often emerge between the second and third administrations of a vaccine.”