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.”
Courtesy UAB Photo
Dr. Jeffrey Curtis
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.
Dr. David T. Rubin
“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.