SARS-CoV-2 booster effect and waning immunity in hemodialysis patients: A cohort study

Abstract Background Dialysis patients are extremely vulnerable to SARS-CoV-2 infection. We recently reported the results of a prospective cohort study measuring serial monthly semi quantitative IgG antibody levels to the SARS-CoV-2 spike protein receptor binding domain in fully vaccinated in-center hemodialysis patients after receiving the BNT162b2 (Pfizer-BioNTech) mRNA vaccination. Methods Prospective cohort study measuring the serologic response of hemodialysis patients to a booster dose of BNT162b2 vaccine at an average of 2, 6 and 11 weeks post vaccination. Results Of 35 hemodialysis patients in the original cohort, 27 (77.1%) received a third dose of BNT162b2. Antibody level significantly increased from pre-booster to 2 weeks post-booster (median (25 th , 75 th percentile) from 59.94 (29.69, 177.8) to 6216 (3806, 11730)), an average increase of 112 fold. Antibody levels dropped to a median of 2654 BAU/mL (1650, 8340) 6 weeks post-booster and to a median of 1444 BAU/mL (1102, 2020) between weeks 6 and 11 post-booster. Antibody levels at 11 weeks remained an average of 40 fold higher than pre-booster levels. Overall, antibody levels declined 47% month to month post-booster. Nine (33%) patients had negative or borderline detectable antibody levels pre-booster and 8 of 9 developed positive (>35.2 BAU/mL) antibody levels post-booster. Those with prior infection had a lower proportional increase in antibody level (51 fold) compared with the median change in COVID naïve patients (144 fold) from pre-booster to 2 weeks post-booster. Conclusions Our data demonstrates that hemodialysis patients obtain a robust humoral response from a third dose of the BNT162b2 vaccine although antibody levels wane over time.