Humoral response after a fourth "booster" dose of a Coronavirus disease 2019 vaccine following a 3-dose regimen of mRNA-based vaccination in dialysis patients.

To the editor:

Despite an initial satisfactory increase in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antispike antibody (Ab) titer after completing a 3-dose regimen in the first set of vaccination in dialysis patients, Ab titer substantially decreases at 6 months in this population. Other authors suggested that for the B.1.1.529 Omicron variant, 3 vaccine doses might be insufficient in in-center hemodialysis patients.

We assessed the dynamics of the anti–SARS-CoV-2 spike protein S1 total Ig Ab (Roche Elecsys immunoassay) of both hemodialysis (n = 17) and peritoneal dialysis (n = 28) patients who received a 3-dose regimen of the mRNA BNT162b2 (Pfizer–BioNTech), followed by a fourth “booster” dose of mRNA vaccine (BNT162b2, n = 43, or mRNA-1273 [Moderna], n = 2), after a median of 7.6 [interquartile range: 7.1; 7.8] months after the third dose (Supplementary Figure S1). Patients with a breakthrough infection (symptomatic or not) before the fourth dose were excluded (Supplementary Figure S2).

In patients (57.8% men, median age 72 [56; 79] years), 15.6% had a history of immunosuppression (Supplementary Table S1). At 15 [14; 22] days after the fourth “booster” dose, antispike Ab titer significantly increased from 923 [369; 2019] to 21,883 [10,234; 42,870] AU/ml (Figure 1 ; Supplementary Figure S3), which corresponds to a 19-fold increase (median) in antispike Ab titer. Ab titer after the fourth dose was 3.4-fold higher (median) than the Ab peak reached after the third dose. Dose 4 appeared well-tolerated (Supplementary Figure S4), and no serious adverse event was observed. After the fourth dose, only 2 patients developed a breakthrough infection (vs. 7 cases of coronavirus disease 2019 after the third dose; Supplementary Table S2).

Figure 1

Kinetics of antispike antibodies. The figure shows the antispike antibody (Ab) levels before, and 1 (M1), 3 (M3), and 6 (M6) months after the third dose of the mRNA BNT162b2 vaccine, and after the fourth vaccine dose (BNT162b2 Pfizer–BioNech or mRNA-1273 Moderna) in dialysis patients. Each point represents individual data. Antibody titers lower than 1 cannot be plotted in the graph because of the logarithm scale. The red points and vertical lines indicate the median with interquartile range. Conversion factor: 1 AU/ml = 1.0288 BAU/ml.

To conclude, our finding shows that a 3-dose regimen of an mRNA-based vaccine with a fourth booster dose appears to produce an important antibody response in dialysis patients, with a significant increase in antispike Ab titer. Long-term follow-up studies are needed to assess if this vaccination strategy elicits a durable and robust protective immune response against SARS-CoV-2 in dialysis patients.

Data Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure

All the authors declared no competing interests.