Third COVID-19 vaccine safe, effective for MS patients with weak response to past doses

A third dose of the COVID-19 vaccine was safe and produced a modest boost in anti-SARS-CoV-2 antibodies in MS patients who experienced a reduced immune response after the first two doses, according to data published in JAMA Neurology.

“Approximately 80% of all patients with MS treated with anti-CD20 therapy or fingolimod have weak humoral immune responses after two doses of messenger RNA (mRNA) COVID-19 vaccines,” Marton König, MD, PhD, of the department of neurology at Oslo University Hospital in Norway, and colleagues wrote.

Researchers sought to determine the safety and immunogenicity of a third dose of mRNA COVID-19 vaccine in fully vaccinated MS patients who were treated with anti-CD20 therapy or fingolimod by conducting an ongoing, observational cohort study. They studied 130 participants (median age 47.5, 74.6% women) from three Norwegian university hospitals, beginning March 23, 2021. Of those, 100 patients received rituximab, 29 received fingolimod and one patient was given ocrelizumab.

Researchers measured antibodies to full-length spike protein from SARS-CoV-2 and the receptor-binding domain (RBD) 3 to 12 weeks after full vaccination and 3 to 5 weeks after revaccination using an in-house, bead-based flow cytometric assay. All patients underwent revaccination and antibody testing before Oct. 1, 2021.

Following full vaccination, results showed mean levels of anti-SARS-CoV-2 spike RBD IgG titer were roughly the same for the anti-CD20 group and fingolimod group. After revaccination, mean levels of anti-SARS-CoV-2 spike RBD IgG titer increased significantly, to 49.4 AU in the anti-CD20 group (P<.001) and to 25.1 AU in the fingolimod group (P=.006).

Of 101 patients given anti-CD20 therapy, 25 were assumed to have protective humoral immunity after revaccination, as well as two of the 29 patients treated with fingolimod. Among those with RBD IgG less than 70 AU after full vaccination, higher absolute lymphocyte count (mean 1262 cells/mm³ vs. 1508 cells/mm³; P=.03) and higher CD19 B-cell counts (in patients receiving anti-CD20 therapy: mean 6 cells/mm³ vs. 25 cells/mm³; P=.03) were associated with the development of protective humoral immunity, compared with those with RBD IgG greater than 70 AU.

At 3 to 5 weeks after revaccination, researchers observed adverse effects in 64 of 101 patients (63.4%) treated with anti-CD20 therapy, but in just 11 of 29 patients (37.9%) treated with fingolimod. The most common complaints were transient local pain and fatigue. No participants reported serious adverse effects following the third dose.

“A third dose of the mRNA COVID-19 vaccine was safe and associated with modestly increased levels of anti–SARS-CoV-2 spike RBD IgG antibodies in patients with reduced protective humoral immunity before reimmunization,” König and colleagues wrote.