SARS-CoV-2 Infection in Vaccinated Maintenance Hemodialysis Patients Despite Anti-Spike Seroconversion: a Report of 3 Breakthrough Cases

Chronically hemodialyzed (HD) patients are vulnerable population during a SARS-COV-2 pandemic.They are at high risk of developing very severe forms of COVID-19 disease.In this article we describe, for the first time to our knowledge, three HD patients (all males, aged 70, 70 and 74 years) vaccinated intramuscularly with two doses of the mRNA BNT162b2 vaccine (BionTech/Pfizer Comirnaty) in whom subsequent breakthrough SARS-CoV-2 infections developed.All patients achieved post-vaccine seroconversion for anti-spike antibodies with IgG titers of 227 AU/mL (cut-off, 13 UA/ml).SARS-CoV-2 infection was diagnosed 28, 44 and 48 days after the second dose of BNT162b2 and confirmed with the polymerase-chain-reaction (PCR) test.Two patients were asymptomatic of COVID-19 and didnʼt require hospitalization.The third patient reported only non-significant drop in oxygen saturation and was hospitalized.All patients were characterized by a moderate or even low post-vaccination neutralizing antibody titer but on the contrary a high production of these antibodies after infection.Perhaps this production of antibodies by memory B cells is responsible for the mild course of the disease and the likely