ABSTRACT
INTRODUCTION: COVID-19 infection is associated with high mortality among hemodialysis patients. Standard vaccine response is generally lower among these patients. The adequate antibody titer response and the outcome of COVID-19 vaccine responders versus non-responders are unknown. METHODS: Hemodialysis patients on maintenance hemodialysis who have received two doses of Pfizer BNT162B2 vaccine were studied. Antibody response was tested after 14 days of the second dose. LIAISON SARS-CoV2 S1/S2 IgG test by DiaSorin (Italy) was used to assess antibody response. Patients were followed between 3 and 7 months after vaccination for COVID-19 infection, hospitalization and death related to COVID-19. FINDINGS: A total of 138 patients received two doses of Pfizer BNT162B2 vaccine. One hundred and twenty-seven patients had adequate response to the vaccine with IgG level ≥ 15 AU/ml versus 11 patients had poor response with IgG level ≤ 15 AU/ml. The response was 92% (127/138). Patient with history of prior COVID-19 infection had higher antibody titer mean of 339 ± 113 versus 157 ± 140 for patient with no prior history of COVID-19. Seven patients in both groups had COVID-19 infection post vaccine. Among the responders, five patients had COIVD-19 infection and two were hospitalized. These two patients had lower antibody titer of 23.9 and 75.2 AU/ml. In comparison, three patients who were not hospitalized had higher antibody titer 96.3, 118, and 319 AU/ml, respectively. In the non-responders one patient was hospitalized and one death occurred with rate of infection of 18%. DISCUSSION: Seropositive patients with low antibody titer might be associated with worse outcome among responders. The ideal antibody titer level among dialysis patient is not known. Also, prior COVID-19 infection is associated with higher response to vaccine with higher antibody titer. All non-responders did not have prior COVID-19 infection. More research is required to further evaluated protective antibody titer.
