1047. Asymptomatic SARS-CoV-2 Infections, BNT162b2 mRNA COVID 19 Vaccine-Related Symptoms, and Correlates of Immunity in Post-Vaccination Breakthrough Infections in the Prospective Assessment of SARS-CoV-2 Seroconversion (PASS) Study

Abstract Background We sought to determine the frequency of asymptomatic SARS-CoV-2 infections, BNT162b2 mRNA COVID 19 vaccine-related symptoms, and correlates immunity in post-vaccination breakthrough infections a prospective cohort healthcare workers. Methods have been conducting single-center, observational study 271 participants were enrolled since August 25, 2020. Testing for spike (S)-specific IgG antibodies is conducted using microsphere-based multiplex immunoassay interpolated against an internal standard curve binding antibody (bAb) units (BAU) has performed on serum samples collected at monthly visits between September 2020 2021, quarterly then. Neutralizing titers wild-type (WT) virus are determined by microneutralization assays Delta Omicron variants lentiviral pseudovirus neutralization assays. For first 6 months, completed symptoms questionnaire every day they had any symptoms. Results 12 diagnosed with SARS-CoV-2, least mild Of 206 evaluated adverse effects after 1st 2nd vaccine doses, no relationship was observed vaccine-associated symptom scores 1 month dose. Longitudinal studies demonstrate that anti-S bAbs decrease from geometric mean (GM) 1929 BAU/mL GM 442 months (P< 0.001, n=187), boosting increases S-specific BAU. While only 5 39 detectable anti-Omicron neutralizing activity 2 vaccinations, booster vaccination resulted all participants. Conclusion Asymptomatic infection likely rare, there severity vaccination, results better protection variant. Ongoing evaluating serological cellular immune responses immediately prior 38 attempt identify will be reported conference. Disclosures John H. Powers, III, MD, Arrevus: Advisor/Consultant|Eicos: Advisor/Consultant|Evofem: Advisor/Consultant|Eyecheck: Advisor/Consultant|Gilead: Advisor/Consultant|GlaxoSmithKline: Advisor/Consultant|OPKO: Advisor/Consultant|Resolve: Advisor/Consultant|Romark: Advisor/Consultant|SpineBioPharma: Advisor/Consultant|UTIlity: Advisor/Consultant|Vir: Advisor/Consultant David Tribble, DrPH, Astra Zeneca: The HJF, support USU IDCRP, funded conduct or augment unrelated Phase III Mab trials as part US Govt. COVID19 response Simon Pollett, MBBS, Timothy Burgess, MPH, AstraZeneca: response.