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Inflammatory bowel disease (IBD) patients' antibody responses to COVID-19 declined over time, especially more than 90 days following infection, Canadian researchers found in a serosurveillance study.

Up to 90 days after COVID-19 diagnosis, 80.8% of IBD patients tested positive for nucleocapsid antibodies, but after 90 days, that number dropped to 21.7%, reported Gilaad G. Kaplan, MD, from the University of Calgary in Canada, and colleagues in a letter to the editor in .

"Many individuals with IBD are immunocompromised by their medical treatments," Kaplan told 番茄社区app. "Moreover, immunosuppression may reduce the formation of antibodies to viruses such as SARS-CoV-2." He explained this population is high-risk for contracting COVID-19.

"These data highlight the importance of vaccination against SARS-CoV-2 even among individuals who were previously diagnosed with COVID-19," he added.

Overall, seropositivity among IBD patients in the study was 1%, while it was 1.8% in the general population of Calgary, "suggesting that patients with IBD were less exposed to SARS-CoV-2 or that serological response postinfection was not as robust as the general population," wrote Kaplan and co-authors.

Seropositivity was also lower than prior IBD studies in both the U.S. (3%) and U.K. (4.3%), potentially due to the "lower prevalence of COVID-19 in the general population in Canada," they noted.

The researchers aimed to evaluate serological responses to COVID-19 in IBD patients, assessing the possibility for a diminished antibody response over time. They built off the work of suggesting infliximab (Remicade) reduced COVID-19 antibody responses in IBD patients. Poor antibody responses from single dose COVID-19 vaccines have also been observed in IBD patients treated with infliximab, the authors noted.

They calculated the time from COVID-19 diagnosis to the time (in days) to serological testing, and the effect of time on either nucleocapsid positive or negative antibody results, by creating a statistical logarithmic regression model adjusted for covariates such sex, anti-tumor necrosis factor (TNF) use, and age. Antibody responses were measured through a validated COVID-19 IgG nucleocapsid protein antibody test.

From October 2020 to April 2021, 324 IBD patients from Calgary were recruited. Participants were divided into two groups, a "serosurveillance" group of 279 patients (median age 48) without a prior diagnosis of COVID-19 and 45 patients who "recovered" from COVID-19 (median age 43).

About 56% to 60% of both groups were women and the majority had Crohn's disease (81% in the serosurveillance group and 64% in the COVID-19 recovered group). About 60% of recovered patients were taking anti-TNF agents compared to 49.5% of the serosurveillance group.

At baseline, 1.08% of the serosurveillance group were nucleocapsid antibody positive compared to 53.3% of the recovered group. Among those who tested positive for nucleocapsid antibodies, 4.2% required hospitalization (one patient from the recovered group).

Authors acknowledged several limitations of their study, including the small sample size and the fact that that they did not test for neutralizing antibodies. Also, the findings cannot be generalized to non-IBD patients who contract COVID-19.

"Our data highlight the importance of studying sustained antibody response over time in order to develop strategies to ensure durable protection and inform public health policy," Kaplan said. "We are also increasing our sample size in order to explore the impact of medications to treat IBD on antibody response."

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