Patient B-Cell Counts at Time of Vaccine Influence COVID-19 Antibody Response

Kyriakos Kirou, MD, DSc, FACP

According to a late-breaking study presented at American College of Rheumatology (ACR) 2021 Convergence, compared to other immunosuppressant agents (ISA), rituximab and belimumab significantly inhibited antibody responses to COVID-19 vaccines in patients with systemic rheumatic disease (SRD).

Kyriakos Kirou, MD, DSc, FACP, and, Jeffrey Zhang-Sun, Hospital for Special Surgery, conducted the study “COVID-19 Vaccine Antibody Responses in Patients Treated with B-Cell Agents Depend on B-Cell Counts at Time of Vaccine”.

The Motivation

Patients with systemic rheumatic disease are at risk for breakthrough infection because they’re not getting adequate immune responses from the COVID-19 vaccine. According to investigators, this is at least partially because of their treatment with immunosuppressive agents.

The consideration of B cell counts could better inform decisions about the timing of vaccination in patients with systemic rheumatic disease, particularly those on rituximab or belimumab, investigators wrote.

Generally, results showed that the lower the B cell counts, the greater the association. Another option to consider is to modify immunosuppressant dosage around vaccination dates.

The Study

The retrospective study took place from April 2021-August 2021. Investigators reviewed chart data from patients with systemic rheumatic disease in Kirou’s practice.

Originally, 88 patients who received full vaccination with either the Pfizer, Moderna, or Janssen vaccines and had received a SARS-COV-2 Spike immunoglobulin G (IgG) antibody test after their final vaccine dose were considered. However, only those who had the Siemens SARS-COV-2 IgG assay were included in order to compare Spike antibody titers between patients (N=60).

The Results

Systemic lupus erythematosus (SLE) diagnosis accounted for almost half of the population study at 48% or 29 out of 60 total patients. 15% of patients had a diagnosis of rheumatoid arthritis (RA), 13% were diagnosed with undifferentiated connective tissue disease (UCTD), and 24% had other diagnoses.

The majority of patients, 67%, had received the Pfizer vaccine while 32% received the Moderna vaccine and 2% received the Janssen vaccine.

Negative Spike antibody responses to the vaccine occurred in 15% of patients, 50% had antibody titers of >20.0, and 35% of patients had titers between 1.0 and 20.0 internal units (IU).

On a scatterplot of B cell counts in patients who received any B cell agent compared with their corresponding Spike IgG titers, a cluster of patients with very low antibody titers was revealed. Much lower antibody responses were seen in patients who received any B cell treatment compared with patients who didn’t.

A B cell count of < 40 in patients around the time of vaccination indicated a much lower Spike IgG titers than patients with B cell counts of greater than or equal to 40, regardless of the B cell agent used.

No significant effect in antibody responses attributable to other immunosuppressant agents or biologic agents was detected. However, investigators found that Moderna vaccination was associated with higher Spike IgG titers than Pfizer vaccination.