MO888: Long-Term Humoral Immune Response Following Full SARS-COV-2 MRNA Vaccination and Booster Dose in Haemodialysis Patients
Authors: León-Póo Mariana , Gallego Valcarce Eduardo , Shabaka Amir , Gruss Enrique , Cordon Alfredo , Maria Cases Corona Clara , Maria Fernandez Juarez Gema 
Published: May 2022

Abstract

BACKGROUND AND AIMS
COVID-19 is associated with an increased mortality in maintenance haemodialysis patients. Considering the baseline immunosuppressed status of this population, humoral immune responses to SARS-CoV-2 vaccination remain to be studied. There is no information regarding sustained immune response in this population after a third booster dose following complete m-RNA vaccination. The aim of our study was to describe the humoral immune response in haemodialysis patients following a complete SARS-CoV-2 vaccine schedule and a third booster dose, and explore the factors associated with a sustained immune response.

METHOD
We conducted a retrospective study in which we included haemodialysis patients with or without (naïve) previous COVID-19 infection. Patients received the following vaccination schedule: two initial doses of m-RNA vaccine with a 4-week interval (complete immunization) followed by a third booster dose at least 4 months after the second initial dose. IgG anti-SARS-CoV-2 spike antibody titles were measured before the first initial vaccine dose and then monthly up to 3 months after the booster dose. We excluded patients without baseline serological samples and those who did not receive the full vaccination schedule.

RESULTS
The study included 182 haemodialysis patients with a mean age of 68.5 ± 14.5 years, 63.2% were males and 14.3% were under immunosuppression, 67.7% were responders to HBV vaccine and 18.1% had been infected with SARS-CoV-2 prior to vaccination.
After the first two vaccine doses, 96.5% developed immediate humoral immune response, and 91.5% remained with positive anti-SARS-CoV-2 spike antibodies after 4 months from complete vaccination. Median antiSARS-CoV-2 spike antibody titles were significantly higher in patients with previous COVID-19 infection and HBV vaccine responders, both immediately (40 000 AU/mL versus 2926 AU/mL, P &lt; 0.001 and 4885 versus 2056 AU/mL, P = 0.003, respectively) and after 4 months from complete vaccination (27 741 versus 663 AU/mL, P &lt; 0.001 and 1356 versus 341 AU/mL, P = 0.001).
In the 4 months between complete initial vaccination and the third booster dose, the mean monthly decrease in antiSARS-CoV-2 spike antibody titles was of 31.8% (±18.9) and was significantly lower in patients with prior COVID-19 infection compared with naïve patients (17.2% versus 34.8%, P &lt; 0.001).
After the third booster dose, 98.2% of patients showed positive anti-SARS-CoV-2 S antibodies, and this proportion remained stable in the following 3 months. Nevertheless, median anti-SARS-CoV-2 spike antibody titles remained higher in patients with prior COVID-19 both immediately and after 3 months. However, we observed a more sustained humoral response after the booster dose, with a lower mean monthly decrease in antibody titles compared with the initial vaccine schedule (31.8% to 22.6%, P &lt; 0.001). This finding was reciprocated in all groups, regardless of prior serological COVID-19 status, HBV vaccine response, age or sex.
Multivariate logistic regression for the risk of a &gt;25% monthly decrease in antibodies showed that prior infection with COVID-19 was a protective factor both after the complete initial vaccination {OR: 0.23, [95% confidence interval (95% CI) 0.06–0.87]} as well as after the third dose (OR: 0.23, 95% CI 0.06–0.81).

CONCLUSION
Vaccination with m-RNA anti-SARS-CoV-2 is effective in eliciting an immediate humoral response in haemodialysis patients, with a progressive reduction in immune response after 4 months particularly in COVID-19 naive patients. A third booster dose enhances the immune response with significantly higher antibody levels and more sustained humoral immune after 3 months in haemodialysis patients.