MO912: Different Immunogenicity of Previous SARS-COV-2 Infection or Comirnaty Vaccine (BNT162B2, BioNTech/Pfizer) in Haemodialysis Patients

Abstract BACKGROUND AND AIMS The pandemic emergency deriving from the SARS-CoV-2 infection has made it necessary to find effective strategies to preserve high-risk populations with severe comorbidities like haemodialysis patients. Adequate vaccination coverage is of vital importance, representing the main weapon to counter the spread of the virus. The purpose of our study was to evaluate the antibody response of our dialysis patients vaccinated with the Comirnaty-BioNTech/Pfizer vaccine in comparison with those with previous infection. METHOD We retrospectively analysed 52 patients referried to the Dialysis Unit of University Hospital G. Martino, Messina, from 2020 to 2021. Of these, 41 patients had never contracted SARS-CoV-2 (group A), while 11 patients had contracted the infection (group B). Serum samples were taken before vaccine administration, 3 months and 6 months after administration. A linear mixed model was performed on the measurements to analyse the difference in antibody response, comparing the values ​​of neutralizing IgG and anti-COVID-19 antibodies during time (Fig. 1). RESULTS The results showed a statistically significant higher titre of anti-spike antibodies in patients with a previous infection (P = 0.003), with a stronger association at 6 months after infection. The linear mixed model showed a significant association over time between infection and antispike (ln U/L) in the univariate model, which was confirmed in the multivariate model {adjSlope: 2.9, [95% confidence interval (95% CI) 1.3–4.6]; P =.001}. No other variables were related to antispike. CONCLUSION These findings can raise novel questions on the role of natural immunity and antibody titre in the haemodialysis population.