<unk> /protection to a virus or other infectious pathogen are measurable signs that a person (or other potential host) is immune, in the sense of being protected against becoming infected and/or developing disease. For many viruses, antibodies and especially neutralizing antibodies serve as a<unk> . So for example, pregnant women are routinely screened in the UK for rubella antibodies to confirm their<unk>  to this infection which can cause serious congenital abnormalities. In contrast for HIV, the simple presence of antibodies is clearly not a<unk> /protection since infected individuals develop antibodies without being protected against disease. The fact that the<unk> /protection remain unclear is a significant barrier to HIV vaccine research. There is evidence that some highly exposed individuals can develop resistance to HIV infection, suggesting that<unk>  and therefore a vaccine is possible. However, without knowing the<unk> , scientists cannot know exactly what sort of immune response a vaccine would need to stimulate, and the only method of assessing vaccine effectiveness will be through large phase III trials with clinical outcomes (i.e. infection and/or disease, not just laboratory markers). A July 2021 study used this predictive marker to validate higher levels of neutralizing antibodies corresponding with lower likelihood of breakthrough infection in COVID-19.
Correlates of immunity
Biosimilar
Social immunity
Modes of toxic action
Introduction to viruses
Tissue tropism
Vaccine ingredients
Physiological effects in space