Serosurveys

A serosurvey is a population-based study that measures the prevalence of antibodies to a particular pathogen in a defined group. By testing blood samples for antibody responses, serosurveys estimate the proportion of individuals who have been exposed to an infection, recovered from it, or been vaccinated, providing indirect information about past transmission.

Typically, serosurveys are cross-sectional or serial cross-sectional studies conducted on representative samples of the population. They may use residual sera from routine testing or actively recruited participants. Laboratory testing relies on antibody assays, such as ELISAs or rapid tests, whose performance is described by sensitivity and specificity. To obtain unbiased estimates of seroprevalence, researchers adjust crude results for test characteristics and, when necessary, account for sampling design and demographic factors.

Interpreting seroprevalence requires careful consideration. A positive antibody result indicates previous exposure or vaccination but does not guarantee current immunity, and antibody levels can wane over time. Seroprevalence reflects cumulative transmission up to the time of sampling and may miss recent changes in transmission dynamics. Limitations include sampling bias, cross-reactivity in assays, geographic and age-related heterogeneity, and logistical or ethical constraints.

Serosurveys have been applied to various pathogens, including HIV, SARS-CoV-2, influenza, dengue, measles, and rubella, to inform public health decisions. They help gauge population immunity, identify transmission hotspots, monitor epidemic progress, and guide vaccination strategies, while being complemented by other surveillance data to provide a fuller picture of disease activity.