Possible Vaccine Outcomes

It is important to realize that scientists are still learning how vaccines might work to prevent HIV infection. An HIV vaccine may be totally successful in preventing any infection in vaccinated people, providing what is known as "sterilizing immunity." Sterilizing immunity may be possible in 100% of the population, or perhaps only in certain groups. In another scenario, a preventive vaccine may not prevent primary infection, but may decrease the possibility of HIV transmission from an infected person who has been vaccinated to another person. Yet another possibility is that a vaccine may not prevent infection entirely, but may slow the course of infection when it occurs. In this case, even if a vaccinated person becomes HIV infected, the vaccine helps that person remain healthier longer. The following list provides details about the variety of ways that scientists believe a preventive HIV vaccine might work.

Sterilizing immunity
  • complete protection from HIV infection
  • no detectable HIV at any time
  • no transmission of HIV to others

Transient infection
  • infection occurs, but the immune system is able to detect and kill off infected cells
  • disease process does not advance, because immune system is able to control the infection
  • no detectable HIV at later times (6-12 months after infection)
  • seroconversion (becoming HIV+) may or may not occur
  • transmission to others might occur within a brief window of time, or might be completely prevented

Long-term controlled infection
  • undetectable or very low viral load (the amount of HIV RNA in a blood sample) throughout life
  • no harmful drop in CD4 cells
  • no immunodeficiency disease progression (HIV does not advance to AIDS)
  • seroconversion (becoming HIV+) likely
  • transmission to others prevented or greatly diminished

Related Link
Multimedia Presentation: Where's the AIDS Vaccine? Laurence Peiperl, M.D., University of Calfornia San Francisco
A fascinating lecture about the challenges of finding an HIV vaccine. Can be heard through RealAudio.