Pfizer COVID-19 Vaccine Immune Responses in Axial Spondyloarthritis Patients

January 13, 2022

A Comment piece was recently published in The Lancet regarding a small study evaluating the immunogenicity of the Pfizer COVID-19 vaccine in 17 axial spondyloarthritis patients on TNF or IL-17A inhibitors. “All patients were managed according to treatment guidelines; secukinumab (150 mg) was administered every four weeks, and adalimumab (40 mg) was administered either every 2 weeks or every three weeks.” Researchers evaluated antibody and T-cell responses against six healthy controls. No participants in the study had been previously infected with SARS-CoV-2, and all participants received two doses of the Pfizer COVID-19 vaccine with three weeks between doses.

Researchers “observed a robust seroconversion in all study participants… [and there were] no significant differences in the proportion of SARS-CoV-2 reactive T cells between the study groups.” Seroconversion is the process of when a viral infection transitions to produce antibodies. T-cell responses were undetectable in 20% of participants in each group.

Results of the study indicate that participants on the TNF inhibitor adalimubab, also used to treat psoriasis, Crohn’s disease, and ulcerative colitis, did not substantially affect the immune response from the Pfizer vaccine. This was also observed for participants on secukinumab, an IL-17A inhibitor. “Patients receiving these biological DMARDs [disease-modifying antirheumatic drugs] were able to develop cellular immune responses after vaccination with the [Pfizer] vaccine, and the overall humoral and cellular immune response did not differ significantly between patients and health individuals.” Cellular immunity is primarily driven by the production of T cells in response to an antigen (in this case SARS-CoV-2). Humoral immunity occurs during the process of adaptive immunity to produce B cell lymphocytes, which produce antibodies against against a specific antigen.

Neutralizing antibody titers were not assessed in this particular study, nor were cellular or humoral immune responses recorded over a period of time past the initial assessment. It is still unclear what the  antibody threshold is for protection against COVID-19.