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 < 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.