1060. Duration of Seroprevalence among Individuals Previously Infected with SARS-CoV-2 and their Household Contacts

Background Serological tests directed against SARS-CoV-2 can provide information about the timing of infection and immunity against the virus. However, the kinetics of the host immune response to SARS-CoV-2 remain poorly understood. We established a household transmission study to analyze the serological responses within households, to determine longitudinal immune responses to infection. Methods From April 2020 to April 2022, we prospectively enrolled 76 households with at least one RT-PCR confirmed case of COVID-19. Participants were asked to provide blood samples at three time points: at baseline within 2 weeks of the index’s diagnosis of COVID-19, and at one- and three-months post-enrollment. Samples were tested for the presence of IgG antibodies against SARS-CoV-2 spike protein via an FDA EUA approved ELISA. Demographics, medical history, and symptomatology were also collected. Results To date, we have analyzed 238 serologic samples from 135 participants, including 82 baseline samples, 89 one-month samples, and 67 three-month samples. At baseline, 67.8% (n=40/59) of all confirmed cases tested positive for SARS-CoV-2 antibodies, which increased to 86.4% (n=57/66) at the one month, and 85.1% at three months (n=40/47). Of those confirmed infected participants that failed to seroconvert at baseline, almost all reported symptoms (n=14/19, 73.7%) and did not have chronic medical conditions (n=17/19, 89.5%). Of the 19, 3 failed to seroconvert by their third visit. All individuals who were fully vaccinated at the time of each visit tested positive for antibodies at baseline (n=26), one-month (n=27), and three-months (n=20). Of those who were not fully vaccinated, 56 (41.1%) were positive for antibodies at baseline, 62 (59.7%) were positive at one -month, and 47 (63.8%) at three-months. Differences in seropositivity rates between pediatric and adult participants, as well as between index cases and household contacts, at each visit were also identified (Table 1). Conclusion Identifying differences in seroprevalence in various demographic groups can provide insight into longitudinal immune responses post-infection. Future analyses on seropositivity among previously infected individuals who received therapeutics may be of interest. Disclosures Andra L. Blomkalns, MD, MBA, Eli Lilly and Company: Grant/Research Support Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Member, DSMB, Pfizer Meningococcal Vaccine clinical trial.