seroepidemiology

Seroepidemiology is a branch of epidemiology that uses measurement of antibodies in blood to study how diseases affect populations. By analyzing the presence or absence of pathogen-specific antibodies, it estimates past exposure, infection spread, and immune status in a community, offering insight beyond what clinical case reporting provides.

Key components include serosurveys, which collect serum samples from a representative population sample, and seroprevalence estimates, the proportion with detectable antibodies. Longitudinal serosurveys can track changes over time. Laboratory assays such as ELISA, immunofluorescence, and neutralization tests detect antibodies of various isotypes (for example IgG or IgM) and, in some cases, neutralizing activity. Distinctions are made between infection-induced and vaccine-induced antibodies when possible.

Applications encompass estimating cumulative incidence and population exposure, assessing vaccine impact and coverage, monitoring outbreak dynamics, and informing public health interventions. Serology can reveal immunity gaps, guide resource allocation, and help evaluate herd immunity thresholds.

Challenges include imperfect test sensitivity and specificity, cross-reactivity between related pathogens, waning antibody levels, and difficulty distinguishing past infection from vaccination. Sampling bias, timing of serosurveys, and ethical considerations around consent and data privacy also affect interpretation. Additionally, serology may not fully reflect protective immunity, since cellular responses can contribute to protection.

Examples of use include HIV and hepatitis B/C surveillance, rubella seroprevalence in women of childbearing age, and SARS-CoV-2 seroprevalence studies to estimate true infection rates.