Although our study focused on pertussis, this unique opportunity for serologic surveillance could be extended to other infectious diseases, including influenza. recent cough illness and pertussis vaccination. The survey was used to distinguish between antibodies induced by vaccination and pertussis infection. Elevated antibodies suggestive of recent infection were found among two adults. The prevalence of undetectable antibodies, suggestive of susceptibility, was 72.3% (95% CI 59.6, 85.1%) among 7C17 year olds, 53.8% (95% CI 26.7, 80.9%) among 1C6 year olds, and 23.3% (95% CI 8.2, 38.5%) among adults. Our ability to rapidly enroll participants and collect satisfactory specimens suggests that seroepidemiologic studies with 1000C2000 participants could efficiently be completed over the 12-day course of the Minnesota State Fair. This setting raises the possibility of efficiently conducting annual population-based seroepidemiologic studies to supplement traditional public health surveillance in estimating disease prevalence, monitoring vaccine impact, and identifying at-risk groups. to isolate serum from blood cells. Centrifuged samples were immediately refrigerated. Specimens were transported on ice to the Minnesota Department of Health Public Health Laboratory (MDHCPHL) for testing at the end of each day. Antibody levels were quantified using an IgG anti-PT ELISA assay that was developed by the Centers for Disease Control and Tiplaxtinin (PAI-039) Prevention and validated at MDHCPHL for use with acute or convalescent serum specimens [25]. The assay measures antibody levels against pertussis toxin, a pertussis-specific antigen that is produced by the bacterium and is ZAK a component of pertussis vaccines. We categorized antibody levels according to commonly used cut-off values, with a concentration above 62.5 IU/mL indicating infection or vaccination within Tiplaxtinin (PAI-039) the past year (Table 1) [26]. An undetected infection was Tiplaxtinin (PAI-039) defined as a participant who met all of the following criteria: (1) had antibody levels 62.5 IU/mL; (2) reported no pertussis vaccination within the past year; (3) reported no diagnosis of pertussis by a healthcare provider within the past year. Participants with undetectable antibody levels ( 5 IU/mL) were considered susceptible [26]. Table 1 Interpretation of IgG anti-PT ELISA results within a population. Our pilot study demonstrates that we could feasibly use the Minnesota State Fair to obtain annual sera samples over the course of a full epidemic Tiplaxtinin (PAI-039) cycle to find a reliable surveillance measure that is indicative of an impending outbreak year. Additionally, demographic-specific trends interpreted in combination with routine surveillance data may highlight a subgroup in which targeted intervention could disrupt sustained transmission between outbreak years. Although cut-off values for serologic pertussis testing are not definitive, focusing on relative changes over time in a single population will produce directly comparable results that should be subject to less uncertainty as we use seroepidemiologic studies to better understand local dynamics of the epidemic cycle of pertussis [26]. In addition to providing estimates of population susceptibility and infection prevalence for infectious diseases, large seroepidemiologic studies conducted on fairgrounds could be used to efficiently monitor vaccine impact [28]. Serologic data can inform public health policy by identifying vulnerable subgroups that may benefit from an adjustment to vaccine recommendations. Importantly, the fixed timing of the state fair each year would control for seasonal effects [29]. Although our study focused on pertussis, this unique chance for serologic monitoring could be prolonged to additional infectious diseases, including influenza. Miller et al. used sera samples collected in two consecutive years to establish an immunity profile in an English human population before and after a wave of influenza illness [30]. The authors concluded that continued serologic studies would be beneficial to understanding the epidemiology of specific subtypes and providing data to inform guidelines for prediction models. State fairgrounds present a logistically simple remedy for such sustained study. We acknowledge that our study sample may not be representative of the state of Minnesota. Metropolitan residents were overrepresented, which is not unexpected given that the fairgrounds are located inside a metropolitan region. Future studies could stratify enrollment based on region of residence or adjust the prospective population to the seven region metro, which consists of over half of the claims human population. Additionally, selection bias in our study is possible if health status or vaccination status impacted participation. Under this assumption, we would expect participants to be less likely to have pertussis and more likely to.