Researchers Stress Importance of Second
COVID-19 Vaccine Dose for Infliximab Users

Steve Cimino

April 07, 2021

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Patients being treated with infliximab had weakened immune responses to the first dose of the ChAdOx1 nCoV-19 (Oxford/AstraZeneca) and BNT162b2 (Pfizer/BioNTech) vaccines, compared with patients on vedolizumab (Entyvio), although a very significant number of patients from both groups seroconverted after their second dose, according to a new U.K. study of patients with inflammatory bowel disease (IBD).

"Antibody testing and adapted vaccine schedules should be considered to protect these at-risk patients," Nicholas A. Kennedy, PhD, MBBS, of the University of Exeter (England) and colleagues wrote in a preprint published March 29 on MedRxiv.

Infliximab is an anti–tumor necrosis factor (anti-TNF) monoclonal antibody that's approved to treat adult and pediatric Crohn's disease and ulcerative colitis, as well as rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and plaque psoriasis, whereas vedolizumab, a gut selective anti-integrin alpha4beta7 monoclonal antibody that is not associated with impaired systemic immune responses, is approved to treat Crohn's disease and ulcerative colitis in adults.

previous study from Kennedy and colleagues revealed that IBD patients on infliximab showed a weakened COVID-19 antibody response compared with patients on vedolizumab. To determine if treatment with anti-TNF drugs impacted the efficacy of the first shot of these two-dose COVID-19 vaccines, the researchers used data from the CLARITY IBD study to assess 865 infliximab- and 428 vedolizumab-treated participants without evidence of prior SARS-CoV-2 infection who had received uninterrupted biologic therapy since being recruited between Sept. 22 and Dec. 23, 2020.

In the 3-10 weeks after initial vaccination, geometric mean concentrations for SARS-CoV-2 anti-spike protein receptor-binding protein antibodies were lower in patients on infliximab, compared with patients on vedolizumab for both the Pfizer (6.0 U/mL [5.9] versus 28.8 U/mL [5.4], P < .0001) and AstraZeneca (4.7 U/mL [4.9] versus 13.8 U/mL [5.9]; P < .0001) vaccines. The researchers' multivariable models reinforced those findings, with antibody concentrations lower in infliximab-treated patients for both the Pfizer (fold change, 0.29; 95% confidence interval, 0.21-0.40; P < .0001) and AstraZeneca (FC, 0.39; 95% CI, 0.30-0.51; P < .0001) vaccines.

After second doses of the two-dose Pfizer vaccine, 85% of patients on infliximab and 86% of patients on vedolizumab seroconverted (P = .68); similarly high seroconversion rates were seen in patients who had been infected with SARS-CoV-2 prior to receiving either vaccine. Several patient characteristics were associated with lower antibody concentrations regardless of vaccine type: being 60 years or older, use of immunomodulators, having Crohn's disease, and being a smoker. Alternatively, non-White ethnicity was associated with higher antibody concentrations.

Evidence Has 'Unclear Clinical Significance'

"These data, which require peer review, do not change my opinion on the safety and efficacy of COVID-19 vaccines in patients taking TNF inhibitors such as infliximab as monotherapy for the treatment of psoriatic disease," Joel M. Gelfand MD, director of the psoriasis and phototherapy treatment center at the University of Pennsylvania, Philadelphia, said in an interview.

"First, two peer-reviewed studies found good antibody response in patients on TNF inhibitors receiving COVID-19 vaccines (doi: 10.1136/annrheumdis-2021-22028910.1136/annrheumdis-2021-220272). Second, antibody responses were robust in the small cohort that received the second dose of a COVID-19 vaccine. We already know that, for the two messenger RNA-based vaccines available under emergency use authorization in the U.S., a second dose is required for optimal efficacy. Thus, evidence of a reduced antibody response after just one dose is of unclear clinical significance. Third, antibody responses are only a surrogate marker, and a low antibody response doesn't necessarily mean the patient will not be protected by the vaccine."

Focus on the Second Dose of a Two-Dose Regimen

"Tell me about the response in people who got both doses of a vaccine that you're supposed to get both doses of," Jeffrey Curtis, MD, professor of medicine in the division of clinical immunology and rheumatology at the University of Alabama at Birmingham, said in an interview. "The number of patients in that subset was small [n = 27] but in my opinion that's the most clinically relevant analysis and the one that patients and clinicians want answered."

He also emphasized the uncertainty around what 'protection' means in these early days of studying COVID-19 vaccine responses. "You can define seroprotection or seroconversion as some absolute level of an antibody response, but if you want to say 'Mrs. Smith, your antibody level was X,' on whatever arbitrary scale with whoever's arbitrary lab test, nobody actually knows that Mrs. Smith is now protected from SARS-CoV-2, or how protected," he said.

"What is not terribly controversial is: If you can't detect antibodies, the vaccine didn't 'take,' if you will. But if I tell you that the mean antibody level was X with one drug and then 2X with another drug, does that mean that you're twice as protected? We don't know that. I'm fearful that people are looking at these studies and thinking that more is better. It might be, but we don't know that to be true."

Debating the Cause of Weakened Immune Responses

"The biological plausibility of being on an anti-TNF affecting your immune reaction to a messenger RNA or even a replication-deficient viral vector vaccine doesn't make sense," David T. Rubin, MD, professor of medicine at the University of Chicago and chair of the National Scientific Advisory Committee of the Crohn's and Colitis Foundation, said in an interview.

"I'm sure immunologists may differ with me on this, but given what we have come to appreciate about these vaccine mechanisms, this finding doesn't make intuitive sense. So we need to make sure that, when this happens, we look to the next studies and try to understand, was there any other confounder that may have resulted in these findings that was not adequately adjusted for or addressed in some other way?

"When you have a study of this size, you argue, 'Because it's so large, any effect that was seen must be real,' " he added. "Alternatively, to have a study of this size, by its very nature you are limited in being able to control for certain other factors or differences between the groups."

That said, he commended the authors for their study and acknowledged the potential questions it raises about the single-shot Johnson & Johnson vaccine. "If you only get one and you're on infliximab, this study implies that maybe that's not enough," he said. "Despite the fact that Johnson & Johnson was approved as a single dose, it may be necessary to think about it as the first of two, or maybe it's not the preferred vaccine in this group of patients."

The study was supported by the Royal Devon and Exeter and Hull University Hospital Foundation NHS Trusts and unrestricted educational grants from Biogen (Switzerland), Celltrion Healthcare (South Korea), Galapagos NV (Belgium), and F. Hoffmann-La Roche (Switzerland). The authors acknowledged numerous potential conflicts of interest, including receiving grants, personal fees, and nonfinancial support from various pharmaceutical companies.

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