Inflammatory bowel disease drug ‘linked to reduced Covid-19 antibody response’

Nina Massey
·4-min read

A commonly prescribed inflammatory bowel disease (IBD) drug may be linked to reduced coronavirus antibody response, research suggests.

According to a new study, infliximab blunts the immune system to Covid-19 infection, potentially increasing the risk of reinfection.

The findings arose from the Clarity study, which recruited 6,935 patients with Crohn’s disease and ulcerative colitis from 92 UK hospitals between September and December 2020.

It found that fewer than half of people with IBD who were treated with the drug had detectable antibodies after SARS-CoV-2 infection, the coronavirus that causes Covid-19.

The authors say an impaired immune response may boost susceptibility to recurrent Covid-19 and help drive the evolution of new variants.

However, they are encouraging people to continue to take their medication as overall Covid-19 risk remains very low.

The researchers say careful monitoring of patients with IBD treated with infliximab, who have been vaccinated against the virus, will be needed to ensure they mount a strong enough antibody response to ward off the infection.

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Clarity study lead Professor Tariq Ahmad, of the University of Exeter Medical School, said: “The poor antibody responses observed in patients treated with infliximab raise the possibility that some patients may not develop protective immunity after Covid-19 infection, and might be at increased risk of reinfection.

“What we don’t yet know is how use of anti-TNF drugs will impact antibody responses to vaccination.”

Around two million people worldwide are prescribed anti-tumour necrosis factor (anti-TNF) drugs, which include infliximab.

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 study, published in the Gut journal, sought to investigate the impact of infliximab on immune responses to SARS-CoV-2 in patients with IBD.

Around 500,000 people across the UK live with IBD, of which ulcerative colitis and Crohn’s disease are the two main forms.

Symptoms include urgent and frequent bloody diarrhoea, weight loss, pain, and extreme fatigue.

At the start of the 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.

In the study, researchers compared antibody responses to SARS-CoV-2 in patients treated with infliximab to an alternative medication, vedolizumab, that blocks inflammatory cells entering the gut without reducing immune responses to infections or vaccinations.

They found that rates of Covid-19 infection and hospital admissions were similar between infliximab and vedolizumab-treated patients.

However, according to the paper, infliximab-treated patients were much less likely to subsequently have a positive antibody test.

Researchers say these findings could therefore not be explained by differences in acquisition or severity of infection alone.

They add that instead, infliximab seemed to be directly influencing antibody responses to infection.

The study also found that rates of positive antibody tests were lowest in participants who were also taking other drugs that suppress the immune system, such as azathioprine, mercaptopurine or methotrexate.

Dr Nick Powell, of Imperial College London, said the team is now exploring the role of other elements of the immune system, which may still protect against reinfection.

He explained: “Although we clearly observed diminished antibody responses in patients taking infliximab, we haven’t yet completed our investigation of T-cell and other protective immune responses against the virus.

“I would expect that even in the presence of less efficient antibody production, infliximab-treated patients will mobilise some protective aspect of their immune system to defend themselves.”

Sarah Sleet, chief executive officer at Crohn’s and Colitis UK, said: “At this stage, the key message is people with Crohn’s and colitis should keep taking their medication to stay well and take the vaccine when offered.

“But we also need research like this to continue. A huge number of people with Crohn’s and colitis have had to contend with the stresses of shielding and social distancing, and it’s vital this group is prioritised in research.”

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