How to not get terribly sick

Assalamualaikum. I hope everyone is well.

I will be going to make Umrah very soon Insha’Allah and I’ve heard that people get very very sick while on the trip and when they come back. This scares me a bit as my immune system is a bit weak, and I am allergic to certain medications that help alleviate symptoms. Any tips of how to not get terribly sick?