Background SARS-CoV-2 breakthrough infections after complete vaccination are increasing whereas their determinants remain uncharacterized. Methods We analyzed two cases of post-vaccination SARS-CoV-2 infections by α and β variants, respectively. For each participant both humoral (binding and neutralizing antibodies) and cellular (activation markers and cytokine expression) immune responses were characterized longitudinally. Results The first participant (P1) was infected by an α variant and displayed an extended and short period of viral excretion and symptom. Analysis of cellular and humoral response 72 h post-symptom onset revealed that P1 failed at developing neutralizing antibodies and a potent CD4 memory response (lack of SARS-CoV-2 specific CD4 + IL-2 + cells) and CD8 effector response (CD8 + IFNγ + cells). The second participant (P2) developed post-vaccination SARS-CoV-2 infection by a β variant, associated with a short period of viral excretion and symptoms. Despite displaying initially high levels and polyfunctional T cell responses, P2 lacked initial β-directed neutralizing antibodies. Both participants developed and/or increased their neutralization activity and cellular responses against all variants, namely, β and δ variants that lasts up to 3 months after breakthrough infection. Conclusions An analysis of cellular and humoral response suggests two possible mechanisms of breakthrough infection: a poor immune response to vaccine and viral evasion to neutralizing antibodies.
【저자키워드】 SARS-CoV-2, Vaccine, immune evasion, variant of concern, Breakthrough infection, 【초록키워드】 neutralizing antibody, immune response, vaccination, Neutralizing antibodies, SARS-COV-2 infection, variant, cytokine, Symptom, CD4, CD8, Symptoms, variants, T cell, Viral, cells, immune responses, T cell responses, Breakthrough infection, SARS-CoV-2 infections, mechanism, binding, IL-2, cellular response, marker, memory response, cellular, Analysis, humoral, Cellular responses, determinant, Activation, post-symptom onset, IFNγ, participant, neutralization activity, cytokine expression, Complete, initial, Result, analyzed, lack, characterized, displaying, 【제목키워드】 COVID-19, BNT162b2,