Response to three doses of the Pfizer/BioNTech BNT162b2 COVID-19 vaccine: a retrospective study of a cohort of haemodialysis patients in France

Abstract

Background: The mortality rate associated with coronavirus disease 2019 (COVID-19) is high among haemodialyzed patients. We sought to describe the serological status of haemodialysis patients having received up to three doses of BNT162b2 mRNA vaccine, and to identify factors associated with a poor humoral response.

Methods: We performed a retrospective, observational study of patients attending a dialysis centre in Antibes, France. One or two of each patient's monthly venous blood samples were assayed for anti-spike (S1) immunoglobulin G (IgG).

Results: We included 142 patients, of whom 124 remained COVID-19-negative throughout the study. Among these COVID-19-negative patients, the humoral immune response rate (defined as an anti-S1 IgG titre ≥1.2 U/ml) was 82.9% after two injections and 95.8% after three injections, and the median [interquartile range] titre increased significantly from 7.09 [2.21; 19.94] U/ml with two injections to 93.26 [34.25; 176.06] U/ml with three. Among patients with two injections, the mean body mass index and serum albumin levels were significantly higher in responders than in non-responders (26.5 kg/m² vs. 23.2 kg/m², p = 0.0392; and 41.9 g/l vs. 39.0 g/l, p = 0.0042, respectively). For the study population as a whole at the end of the study, a history of COVID-19, at least two vaccine doses, and being on the French national waiting list for kidney transplantation were the only factors independently associated with the anti-S1 IgG titre.

Conclusions: Dialysis patients vaccinated with two doses of BNT162b2 might not be sufficiently protected against SARS-CoV-2 and so should receive a third (booster) dose.

Trial registration: The present retrospective study of clinical practice was not interventional and so was not registered.

Keywords: COVID-19; Comirnaty; Haemodialysis; SARS-CoV-2; Vaccine.

Fig. 1

Study timeline. It should be noted that not all participants received three doses of vaccine, and that the vaccination dates varied from one participant to another. Hence, the figure shows the sequence of events for a typical participant with three doses and two serology assays

Fig. 2

Study flow chart

Fig. 3

Individual anti-S1 Ig titres for COVID-19-negative patients. Data are shown as a function of the number of doses of vaccine received. Each grey line represents the change in an individual patient’s titre between the first and second serology assays (Ser₁ and Ser₂). The thick, black line was derived by non-parametric, locally estimated smoothing; it illustrates the trend for the group

Fig. 4

Correlation between the anti-S1 Ig titre and age. Data are shown for patients with two or three doses of vaccine (n = 111) for the first (a) and second (b) serology assays

Fig. 5

Correlation between the anti-S1 Ig titre and the anti-HBV titre. Data are shown for the first (a) and second (b) serology assays