Low Levels of Protective Humoral Immunity Following Mild or Asymptomatic Infection With SARS-Cov-2 in a Community-Based Serological Study (WP-21-21)
Thomas McDade, Amelia Sancilio, Richard D’Aquila, Brian Mustanski, Lauren Vaught, Nina Reiser, Matthew Velez, Ryan Hsieh, Daniel Ryan, Rana Saber, Elizabeth McNally, and Alexis DemonbreunThe degree of protective humoral immunity after mild or asymptomatic SARS-CoV-2 infection is not known. The researchers measured antibody-mediated neutralization of spike protein-ACE2 receptor binding—a surrogate measure of protection against SARS-CoV-2 infection—in a large and diverse community-based seroprevalence study. Comparisons were made across three groups of seropositive participants that differed in the severity of infection and engagement with clinical care (N=790). The clinical group was seropositive for prior infection, symptomatic, and diagnosed with COVID-19 by a healthcare provider. The symptomatic group was seropositive and reported one or more symptoms of infection but received no clinical care. The asymptomatic group was seropositive but reported no symptoms. 86.2% of all infections were mild or asymptomatic; 13.8% received clinical care. Of the clinical cases, 96.3% were outpatient; only 3.7% required hospitalization. Moderate or high levels of neutralizing activity were detected following 27.5% of clinical infections, in comparison with 5.4% of symptomatic and 1.5% of asymptomatic infections. The majority of infections in the general population are mild or asymptomatic and likely result in low levels of antibody-mediated protective immunity.