Clarity IBD

What this research looked at

The CLARITY IBD researchers looked at how some medicines used to treat Crohn’s and Colitis affect COVID-19 infection and vaccine response. The study looked at antibody levels in people treated with infliximab after receiving two or three COVID-19 vaccine doses. They did this by comparing to people treated with vedolizumab, a medicine which doesn’t affect immune response to infection or most vaccines.

Your body makes antibodies when you get an infection, like COVID-19, or after you have had a vaccine. Antibodies, along with other parts of the immune system, help your body to fight the infection.

Their results highlight why some people with Crohn’s and Colitis need extra doses of a COVID-19 vaccine.

The researchers also looked at how the medicines used to treat Crohn’s and Colitis influence how long people carry the COVID-19 virus for and rates of long COVID.

What the researchers found

Antibody responses after two or three doses of COVID-19 vaccine

After two doses of vaccine, people taking vedolizumab generally had a higher level of antibodies compared to people taking infliximab.

A third dose of the COVID-19 vaccine boosted levels of antibodies in both people taking infliximab and people taking vedolizumab. However, people taking infliximab had lower antibody levels than the people taking vedolizumab.

Breakthrough infections

Some people who are fully vaccinated against COVID-19 will still get COVID-19 if they are exposed to the virus. This is called a breakthrough infection. The latest CLARITY results found that breakthrough infections after a second or third dose of the COVID-19 vaccine were more common and happened earlier in people taking infliximab compared to the people taking vedolizumab. The breakthrough infections were mostly due to the Omicron variant. Breakthrough infections were also more common in people who had received the AstraZeneca vaccine for doses one and two.

Hospitalisation

It was uncommon for people involved in the CLARITY study to have to go to hospital if they had COVID-19. 1.2% of people involved in the study were hospitalised.

These were the results from the part of the CLARITY study that Crohn’s & Colitis funded. If you would like to read more about other parts of the study, funded by other organisations, see our CLARITY IBD information page.

What the researchers think this could mean for people with Crohn's and Colitis

The CLARITY results are an important step in helping us understand how different medicines for Crohn’s and Colitis affect a person’s response to COVID-19 and to vaccines.

This is important because it may affect how doctors treat COVID-19 in some people. For some people with Crohn’s or Colitis this may mean they are offered further booster vaccines and treatments for COVID-19. Read more about vaccines and treatments at our COVID-19 information hub.

Long COVID

Some people experience troublesome symptoms of COVID-19, like fatigue and breathlessness, for longer than a few months. This condition is called long COVID. The researchers of this study are continuing to explore and analyse how long COVID affects people with Crohn’s and Colitis. They want to find out how common it is and if there are any specific risk factors for developing long COVID in people with Crohn’s and Colitis. 

Who is leading this research: Dr Tariq Ahmad, Royal Devon and Exeter NHS Foundation Trust
Our funding: £43,427.42
Duration: 10 months
Official title of application: ImpaCt of bioLogic therApy on saRs-cov-2 Infection and immuniTY (CLARITY IBD)