Crohn's and ulcerative colitis increase flu threat. What you should know


With flu season behind us – or ahead of us, depending on your perspective – the possibility of contracting the disease is currently low. For people at high risk of complications, however, the threat of flu remains very real. That includes those with inflammatory bowel disease.

Caused by the body’s inflammatory response, inflammatory bowel disease – known individually as Crohn’s disease and ulcerative colitis – is often treated with medications that suppress the immune system. That means the flu can more easily take hold and do damage.

Here, Dr. Jenny Sauk, an assistant clinical professor of medicine, answers some questions about the flu and ulcerative colitis and Crohn’s disease. Sauk is part of the Vatche and Tamar Manoukian Division of Digestive Diseases at the David Geffen School of Medicine at UCLA.

But first a short primer: Crohn’s disease causes inflammation and irritation within the intestinal tract, usually the end of the small intestine, and over time, scarring within the intestine. Ulcerative colitis causes inflammation in the inner lining of the large intestine, including the colon and rectum. Both conditions can cause abdominal pain and frequent diarrhea. Now to the questions…

Jenny Sauk of UCLA
Dr. Jenny Sauk

What do diseases of the intestines have to do with the flu?

People with Crohn’s disease or ulcerative colitis who are on immunosuppressive medications can have increased susceptibility to infections, including the flu and pneumonia. These immunosuppressive medications can be important to reduce inflammation and symptoms associated with the disease. However, they can also suppress the ability of a person’s immune system to fight off infections.

Taking precautionary measures such as receiving appropriate vaccinations can decrease the chance of developing infections while on immunosuppressive therapy.

Should people with Crohn’s disease or ulcerative colitis get the flu shot as early as possible – or wait a while to see how bad the flu season is?

People who are on immunosuppressive medications should definitely be considered a high-risk group. That means they should get the shot as soon as possible – and that they should have priority access to influenza vaccinations.

What type of immunization should they get?

All patients with inflammatory bowel disease should receive the inactivated influenza vaccine – not the nasal spray flu vaccine, which is a live, attenuated influenza virus – regardless of whether he or she is on an immunosuppressive medication.

Are there any special steps that people with Crohn’s disease or ulcerative colitis should take to protect their health during flu season? Or any time of year?

People with Crohn’s disease or ulcerative colitis should receive the inactivated intramuscular influenza vaccination annually during flu season. In North America, flu season is typically from September to May, with peak months in January and February. People may worry that the influenza vaccine can trigger a flare, but studies and expert consensus suggest that the influenza vaccine does not exacerbate disease activity.

General precautionary measures such as avoiding sick contacts, washing hands frequently with soap and water and disinfecting surfaces that may be contaminated with germs are also helpful.

What should someone with inflammatory bowel disease do if they catch the flu?

If a person catches the flu, he/she should limit contact with others as much as possible to keep from infecting others. If a person has the flu, treatment within 2-3 days of symptom onset with Tamiflu or Relenza may decrease the severity or shorten the course of the flu by a few days.


Learn more about the UCLA Vatche & Tamar Manoukian Division of Digestive Diseases.