MO855: Humoral Immunity Against Covid-19 6 Months After the Pfizer BNT162B2 Vaccine in Haemodialysis Patients: Data From 5 Dialysis Units. Is There a Role for HDF in the Covid-19 Pandemia?
Authors: Chuva Teresa , Teresa Santos Maria , Gonçalves Francisco , Lemos Costa Luísa , Alves Elisabete , Neves Inês , Paiva Ana , Carvalho Berta , Sousa Tânia , Rmalheiro António , Maximino Costa José , Vila-Afonso Luísa , Vidal Pinheiro Luís , Corrêa Otília , Loureiro Alfredo 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Haemodialysis (HD) patients tend to be old, have weakened immune systems and suffer from multiple comorbidities, making them particularly prone to infections and death by the Coronavirus disease 2019 (COVID-19). Global vaccination against SARS-CoV2 has been underway, but long-term data in dialysis patients are still scant.
We aimed to study the seroconversion with the Pfizer BNT162b2 vaccine in HD patients of 5 Dialysis Centres after the first 2 doses and monitor the immune responses and clinical data during the following 7 months. We also investigated the security of the vaccine.

METHOD
We included 404 patients on chronic HD. All patients received 2 shots of the Pfizer BNT162b2 vaccine, separated by 21 days. Serologic tests were run using Quant II IgG anti-Spike SARS-CoV-2 assay by Abbott. Blood was drawn 21 days after the first dose (D22), 21 days after the second dose (D43), 3 and 6 months after the first dose (M3 and M6, respectively). We asked the patients to answer written questionaries about the symptoms reported during the 7 days after each vaccination.

RESULTS
60.6% of our patients were male and the median age was 70 years (min 19, max 97). 26 patients (6.4%) had previously been infected with COVID-19. 6 of them (23.1%) needed hospitalization. At 7 months follow-up, there were 3 new cases and 1 death (the one who died had negative antibody counts at M3). Maximum response to the vaccine was seen at D43, with 97.3% of the patients showing positive antibody titers. At 6 months, 91.5% still had positive antibodies. As is reported in Table 1, the following patients had higher antibody titers at D43 and M6: patients with COVID-19 before the first vaccine, younger patients, patients with higher albumin levels, patients on HDF versus HD. Patients on HDF had higher titers at all moments during the 6 months (Figure 1). Patients with cancer without antineoplasic treatment in the last 6 months showed lower rates of seroconversion at D43: OR: 0.117 [95% confidence interval (95% CI) 0.016–0.863]} and M6 (OR: 0.203, 95% CI 0.049–0.842]. Patients whose levels of C-reactive protein was ≤ 2.8 mg/dL had more probability of seroconversion at D43 (OR: 7.840, 95% CI 1.839–33.419; P &lt; 0.005) as well as those with a higher (better) Karnofsky scale (OR 1.062, 95% CI 1.016–1.110).
43.4% of the patients reported at least one side effect after the first shot and 64.6% after the second shot. A total of 69.1% had at least one-side effect on the first or second shot. All the reported reactions were mild and transitory.

CONCLUSION
Patients on HD respond surprisingly well to anti-COVID-19 vaccination and present only mild side effects. Further studies should analyze the impact of HDF on immune responses, since our work suggests that this type of dialysis may have a positive and protective long-term role on this population.