Updated: April 27, 2021 10:36:02 am
People who take a commonly-prescribed drug for inflammatory bowel disease (IBD) should not assume they are protected after a first dose of Covid-19 vaccine, say the authors of a large-scale study that 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-tumour necrosis factor (anti-TNF) biologic drug, prescribed to around two million people worldwide. (One of the brand names under which infliximab is marketed is Remicade, which has got regulatory clearance in India.) Anti-TNF drugs are effective treatments for immune-mediated inflammatory diseases, but by suppressing the immune system, they can reduce vaccine effectiveness and increase risk of serious infection, the researchers have suggested.
Led by the University of Exeter and the Royal Devon and Exeter NHS Foundation Trust, and published in the journal GUT, the paper is an output from the CLARITY Study is funded by the UK National Institute of Health Research (NIHR) and Crohn’s and Colitis UK. The research found that people treated with infliximab had significantly lower concentrations of antibodies, when compared to 428 people on an alternative treatment, vedolizumab.
For a vaccine to be effective, it needs to trigger a sufficient number of virus-targeting antibodies to prevent any subsequent infection.
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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, 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.
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.
The two main forms of IBD are ulcerative colitis and Crohn’s disease. Symptoms include urgent and frequent bloody diarrhoea, weight loss, pain, and extreme fatigue.
Source: University of Exeter
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