People who take infliximab for inflammatory bowel disease (IBD) should not assume they are protected after a first dose of COVID-19 vaccine, after a large-scale study found many had poor antibody responses. The research measured antibody responses after vaccination with the Pfizer/BioNTech or the Oxford/AstraZeneca COVID-19 vaccine in 865 people treated with infliximab, an anti-tumor necrosis factor (anti-TNF) biologic drug. The research found that people treated with infliximab had significantly lower concentrations of antibodies, when compared to 428 people on an alternative treatment, vedolizumab.
The paper from the study, ‘Infliximab is associated with attenuated immunogenicity to BNT162b2 and ChAdOx1 nCoV-19 SARS-CoV-2 vaccines’, published in the journal Gut, was led by the University of Exeter and the Royal Devon and Exeter NHS Foundation Trust. The paper is an output from the CLARITY Study, funded by the NIHR and Crohn's and Colitis UK.
The CLARITY study recruited 6,935 patients with Crohn's disease and ulcerative colitis from 92 UK hospitals between September and December 2020, to investigate the impact of these drugs on COVID-19 susceptibility and protective immunity that follows infection or vaccination. Previously, the study found that infliximab blunts the immune system to COVID-19 infection, potentially increasing the risk of reinfection.
After a single dose of vaccine, only about one third of participants (103 of 328) treated exclusively with infliximab generated adequate levels of antibodies to the virus for the vaccine to be considered effective. In participants simultaneously taking infliximab and immunomodulator drugs, such as azathioprine or methotrexate, the levels of antibodies were even lower after a single vaccine dose; only 125 of 537 met the threshold of a positive antibody test.
However, in a sub-group of people who had previously been infected with COVID-19, and also in the few patients studied who had already had a second dose of vaccine, the vaccine-triggered antibody responses rose significantly, indicating an effective response after two exposures. Based on these observations, the researchers conclude that people taking anti-TNF drugs should be considered a priority for a second vaccination.
CLARITY study lead, Dr Tariq Ahmad, said the current findings had important implications for people treated with anti-TNF therapy, particularly for those also treated with an immunomodulator: "Poor antibody responses to a single dose of vaccine exposes these patients to a potential increased risk of COVID-19. However, we found much higher antibody levels in people vaccinated after a previous COVID-19 infection and in the small number of patients who had received two vaccine doses suggesting that all patients receiving these drugs should be prioritized for optimally timed second doses."
At the start of the COVID-19 pandemic the UK Government advised that patients taking anti-TNF medicines could be at increased risk of complications from coronavirus. All were advised to follow strict social distancing measures, and some, depending on the severity of their condition, were advised to shield.
"Although we know that this has been an incredibly difficult time for people with IBD, our research indicates that people treated with infliximab should consider that they are not protected from COVID-19 until they have had both doses of a vaccine and should continue to practice enhanced physical distancing and shielding if appropriate,” added study co-author, Dr Nick Powell from Imperial College London.
In the study, a small sub-set of patients showed no antibody response even after two exposures to COVID-19. The study also found evidence that antibody responses were lower in current smokers and participants aged 60 or older, but higher in non-white participants. These findings warrant further investigation in larger studies before firm conclusions can be drawn.
“Our findings come as countries across Europe are opting to delay the second dose of vaccine. We recommend prioritising second doses to patients taking anti-TNF drugs, who will remain at high risk after their first dose,” commented study co-author, Dr James Goodhand from the University of Exeter. "Further data are needed to investigate whether we should be testing antibody concentrations after two doses to identify the small number of patients who have not responded well to vaccination."
"This is the first robust evidence that people with Crohn's and Colitis - who may need to take specific drugs to suppress their immune system - do not develop the expected antibodies after their first vaccination dose, although a second dose does improve antibody levels,” warned Sarah Sleet, Chief Executive of Crohn's & Colitis UK. “With one in five not developing antibodies even after two doses, these people will be desperately worried that they remain at risk of catching COVID–19 and may develop a more serious illness at a time when shielding has ended. We need urgent research on the optimal time between the first and second jabs, and the need to be prioritised for any booster jab this Autumn."