SARS-CoV-2 infection in vaccinated maintenance hemodialysis patients despite anti-spike seroconversion: a report of 3 breakthrough cases

Chronically hemodialyzed (HD) patients are at a high risk of developing very severe forms of COVID-19 disease. In this article we describe three HD patients (all males, aged 70, 70 and 74 years) vaccinated intramuscularly with a two-dose 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 445, 227 and 92.5 AU/mL (cut-off, 13 AU/mL) case 1, 2 and 3 respectively. SARS-CoV-2 infection was diagnosed 44, 28 and 48 days after the second dose of BNT162b2 and confirmed with the polymerase-chain-reaction (PCR) test. Two asymptomatic patients underwent this test because of their direct contact with a person with confirmed COVID-19. The third patient reported only a non-significant drop in oxygen saturation, and was hospitalized (case 3). All these patients were characterized by a low post-vaccination neutralizing antibody titer and a high production of these antibodies after falling ill (795, 845 and 5770). Perhaps this production of antibodies is responsible for the mild course of the disease, and the likely reduction of mortality. These breakthrough cases in no way undermine the importance of the vaccinations, and on the contrary argue for their urgency.