The general stages of<unk>  for hepatitis B, where the line of detectability indicates seropositivity In immunology,<unk>  is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination. During infection or immunization, antigens enter the blood, and the immune system begins to produce antibodies in response. Before<unk> , the antigen itself may or may not be detectable, but the antibody is absent. During<unk> , the antibody is present but not yet detectable. After<unk> , the antibody is detectable by standard techniques and remains detectable unless the individual seroreverts. Seroreversion, or loss of antibody detectability, can occur due to weakening of the immune system or waning antibody concentration over time.<unk>  refers the production of specific antibodies against specific antigens, meaning that a single infection could cause multiple waves of<unk>  against different antigens. Similarly, a single antigen could cause multiple waves of<unk>  with different classes of antibodies. For example, most antigens prompt<unk>  for the IgM class of antibodies first, and subsequently the IgG class.<unk>  rates are one of the methods used for determining the efficacy of a vaccine. The higher the rate of<unk> , the more protective the vaccine for a greater proportion of the population.<unk>  does not inherently confer immunity or resistance to infection. Only some antibodies, such as anti-spike antibodies for COVID-19, confer protection. Because<unk>  refers to detectability by standard techniques, seropositivity status depends on the sensitivity and specificity of the assay. As a result, assays, like any serum test, may give false positives or false negatives and should be confirmed if used for diagnosis or treatment.
Seroconversion
Reverse tolerance
Cross-tolerance
Sensitization 
Recrudescence
Peripheral tolerance
Antigenic escape
Cross-resistance