Re: Would it Be Possible to Develop a Vaccine That is 100% Effective?

Anything is possible. But to answer your question, we would have to define more precisely what you mean by 91% effective. It could mean protecting 91% of people from infection. It could mean preventing disease (severe immune deficiency) from developing in 91% of people who get infected. It could mean protecting 100% of vaccinated people from 91% of the strains of HIV-1 in the world, but not providing protection against the other 9% of strains.

As far as I know, there was no HIV vaccine developed by the USA army, or any other army. The VRCO1 and VRCO2 antibodies are not a vaccine, they are more like an antiserum. People would have to be injected with these antibodies every day to be protected from infection. Developing a vaccine that would cause people to produce their own antibodies that bind to the same virus sites that VRCO1 and VRCO2 bind to, would be the challenge.

Right now, there are many vaccines that protect macaques form dying when they are injected with rapidly lethal strains of macaque immunodeficiency virus. But protecting from infection is much more difficult and perhaps impossible.

References:
Zhou T, Georgiev I, Wu X, Yang ZY, Dai K, Finzi A, Kwon YD, Scheid JF, Shi W, Xu L, Yang Y, Zhu J, Nussenzweig MC, Sodroski J, Shapiro L, Nabel GJ, Mascola JR, Kwong PD. (2010) Structural basis for broad and potent neutralization of HIV-1 by antibody VRC01. Science. 329(5993):811-7.

Tao B, Fultz PN. (1995) Molecular and biological analyses of quasispecies during evolution of a virulent simian immunodeficiency virus, SIVsmmPBj14. J Virol. 69(4):2031-7.