MS patients treated with rituximab may receive COVID-19 vaccine as soon as possible

Rituximab-treated patients with MS may be vaccinated for COVID-19 as soon as possible, researchers reported in JAMA Network Open.

Andreas Tolf, MD, of the department of medical sciences at Uppsala University in Sweden, and colleagues conducted a prospective cohort study from Jan. 21 to Dec. 1, 2021, and analyzed data from 67 participants with planned or ongoing treatment with rituximab.

Researchers assessed serological vaccine responses by measuring quantitation of anti-spike IgG antibodies and anti-receptor-binding domain (RBD) IgG antibodies, as well as their neutralizing capacities.

Among the 60 patients currently receiving rituximab (49 women; mean age, 43 years), the median disease duration for MS was 9 years (range, 1-29 years), and the median drug dose was 2,750 mg (range, 500-10,000 mg). Vaccine responses were determined before vaccination with tozinameran and 6 weeks after.

Researchers established cutoff values for anti-spike IgG (264 binding antibody units/mL) and anti-RBD IgG (506 units/mL) to determine the proportion of patients who had a positive response, indicated by an increased number of B cells. A cutoff for B-cell count of at least 40/µL was associated with an optimal serological response.

Six months after the last rituximab infusion, data on B-cell counts were available for 48 patients, and 29 (60%) had a B-cell count of at least 10/µL. Of those 29 patients, 26 (90%) had positive results for anti-spike IgG antibodies, 21 (72%) for anti-RBD IgG antibodies, and 27 (93%) developed antibodies with greater than 90% inhibition of angiotensin-converting enzyme 2.

“These results favor early vaccination without considering time from last infusion or B-cell count because some patients generated a functional serological response anyway, and T-cell responses appeared to develop independently of B-cell count,” the authors wrote. “The results also suggest that an additional vaccine dose may be considered when the B-cell count reaches 40/µL to ensure that as many patients as possible will generate an adequate vaccine response.”