In a cohort of 417 persons who had received the second dose of BNT162b2 (Pfizer–BioNTech) or mRNA-1273 (Moderna) vaccine at least 2 weeks previously, the authors identified 2 women with vaccine breakthrough infection. Despite evidence of vaccine efficacy in both women, symptoms of coronavirus disease 2019 developed, and they tested positive for SARS-CoV-2 by polymerase-chain-reaction testing. Viral sequencing revealed variants of likely clinical importance, including E484K in 1 woman and three mutations (T95I, del142–144, and D614G) in both. These observations indicate a potential risk of illness after successful vaccination and subsequent infection with variant virus, and they provide support for continued efforts to prevent and diagnose infection and to characterize variants in vaccinated persons.

This study analyzed antibody functions in 52 asymptomatic infected individuals, 119 mild and 21 hospitalized COVID-19 patients. Anti-Spike IgG, IgA and IgM levels with the S-Flow assay and map IgG-targeted epitopes by Luminex were measured. Neutralization, complement deposition and Antibody-Dependent Cellular Cytotoxicity (ADCC) were evaluated and showed that COVID-19 sera mediate complement deposition and kill infected cells by ADCC. Sera from asymptomatic individuals neutralize the virus, activate ADCC and trigger complement deposition. Antibody levels and functions are lower in asymptomatic individuals than in symptomatic cases. Antibody functions are correlated, regardless of disease severity. Overall, asymptomatic SARSCoV-2 infection elicits polyfunctional antibodies neutralizing the virus and targeting infected cells.