My daughter has traveled to South America a few times for archeological digs, and they give her medication to help ward off traveler's diarrhea from her GP. She said her coworkers who didn't take it became ill, but she actually did fine while avoiding foods and water that could be contaminated the whole time she was down there. All that said, she is healthy and I am uncertain of the probability or percentage that contracting TD can happen to those compromised by a chronic disease such as ankylosing spondylitis while on biological medication. Searching for some insight, I did find an article published in 2018 with some info stating:
Results
"There is a paucity of literature in this area, however, it is apparent that travel-related infection risk is increased in patients on biologic therapy and when illness occurs they are at a higher risk of complication and hospitalization. Patients in receipt of biologic agents are deemed as having a high level of immunosuppression—live vaccines, including the yellow fever vaccine, are contraindicated. Inactivated vaccines are considered safe; however, vaccine response can be attenuated by the patient’s biologic therapy, thereby resulting in reduced vaccine effectiveness and protection."
Conclusions
"Best practice requires a collaborative approach between the patient’s primary healthcare physician, relevant specialist and travel medicine expert, who should all be familiar with the immunosuppressive and immunomodulatory effects resulting from the biologic therapies. Timing of vaccines should be carefully planned, and if possible, vaccination provided well before established immunosuppression."
https://academic.oup.com/jtm/article/25/1/tay018/4934912
I hope this sheds some light on the topic. As well, I hope others chime in on this topic with some experiences relating to traveling and being on biological medication. Wishing you safe and healthy travels. Warmly - Rebecca (community moderator)