# A274 COVID-19 INFECTION RISK BETWEEN VACCINATED PATIENTS WITH ULCERATIVE COLITIS AND CROHN’S DISEASE : A RETROSPECTIVE COHORT STUDY IN TAIWAN

## TL;DR

This study found that vaccinated ulcerative colitis patients had a higher risk of contracting COVID-19 compared to vaccinated Crohn’s disease patients in Taiwan.

## Contribution

The study is the first to compare post-vaccination COVID-19 infection risks specifically between ulcerative colitis and Crohn’s disease patients.

## Key findings

- Vaccinated ulcerative colitis patients had a 1.95 to 2.78 times higher risk of COVID-19 infection compared to Crohn’s disease patients.
- Most infected patients had mild symptoms, with only one hospitalization reported.
- The number of vaccine doses showed a trend toward reduced infection risk, but medication was not a significant factor.

## Abstract

The effectiveness of coronavirus disease 2019 (COVID-19) vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients with inflammatory bowel disease (IBD) is well established, but it is not clear whether patients with ulcerative colitis (UC) and Crohn’s disease (CD) have different risks of COVID-19 infection after vaccination.

The aim of this study was to compare the risk of COVID-19 infection after vaccination in patients with UC and CD. Moreover, we also investigated risk factors related to COVID-19 infection and collected data on any adverse events and disease symptoms.

We conducted a retrospective cohort study in adult IBD patients who had received at least two doses of COVID-19 vaccination and compared the prevalence of infection between UC patients and CD patients using the medical records of China Medical University Hospital between 1 January 2020 and 31 March 2023. All data management and odds ratios calculations were performed using version 9.4 of SAS software (SAS Institute, Cary, NC, USA).

Total 169 IBD patients (96 with UC, 73 with CD) were included in this study. UC patients were older than CD patients (44.92±13.72 vs. 37.27±15.27 years, p=0.0008)(Table 1). A high proportion were male (IBD 70.41%; UC 65.63%, and CD 76.71%). Most (57.4%) received three doses of COVID-19 vaccines. Azathioprine, steroid, and mesalazine medication histories were different between the groups (pampersand:003C0.05). COVID-19 infection prevalence was 49.11% (UC 56.25%, CD 39.73%; p=0.0333) (Figure 1). Logistic regression analysis suggested UC patients had an odds ratio of 1.95 (95% CI=1.05-3.62) and adjusted odds ratio of 2.78 (95% CI=1.20-6.44) for COVID-19 infection compared to CD patients, indicating a 1.95-fold to 2.78-fold higher risk (Figure 2). There was a trend towards a decreasing risk of COVID-19 infection with increasing number of vaccine doses. Medication was not identified as a risk factor. (Figure 3)

Our study identified a greater risk of COVID-19 infection in vaccinated patients with UC than those with CD. However, most patients who became infected with COVID-19 did not have severe symptoms and only one case was hospitalized. The mortality rate of COVID-19 in IBD patients is not specifically higher than the general population. Supporting the view that SARS-CoV-2 vaccination is effective in patients with IBD.

Odds ratios (95% confidence interval) for logistic regression model predicting COVID-19 infection among vaccinated IBD patients

Figure 1. The medications used before COVID-19 infection between vaccinated patients with ulcerative colitis (UC) and Crohn’s disease (CD).

Figure2. The prevalence of COVID-19 infection between vaccinated patients with ulcerative colitis (UC) and Crohn's disease (CD).

Figure 3. The symptoms after COVID-19 infection between vaccinated patients with ulcerative colitis (UC) and Crohn's disease (CD).

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