development of antibodies in the blood that were not there before vaccination.
After infection, the body develops antibodies to that particular infection. When antibodies can be detected in the blood, seroconversion has happened. The time between becoming infected and having detectable levels of antibodies in the blood is called the window period. For HIV, the window period is up to 3 months.
Development of detectable antibodies to HIV in the blood serum as a result of infection. It may take several months or more after HIV transmission for antibodies to the virus to develop. After antibodies to HIV appear in the blood, a person will test positive in the standard ELISA test for HIV.