My son was diagnosed just before turning 17 years old. His initial treatment was six weeks of EEN (exclusive enteral nutrition) and a week of IV flagyl. Following the six weeks of EEN, he was kept on supplemental EN - a regular diet (with a few restrictions like seeds, nuts, etc.) and half of the EEN amount he'd been taking during the exclusive period. (Exclusive period he was ingesting 3000 cal/night (he used NG tube overnight), during supplemental phase, he ingested 1500 cal/night, 5 nights/week).
For the next 1.5 years, this was his only treatment (also nexium on nights he used NG tube because NG tube caused him heartburn).
EEN took him into remission, supplemental EN kept him in "clinical" remission. This means he had no outward signs of crohns. He felt good, looked good, gained tons of weight back, etc. However, MRIs continued to show simmering inflammation.
Upon transfer to an adult GI, the new GI was not comfortable with the simmering inflammation and believed it was only a matter of time until there was a problem and he put my son on remicade.
I hated the thought and I'd loved that his only treatment thus far had no side effects! But, my son was leaving to go away to university and was 18 at that time. On top of his GIs advice, I gave my son all my pro and con reasons for remicade and let him make the decision. He did not want to risk surgery or a flare that would interfere with his school and chose to add remicade.
It's now been over 7(??) years and he's doing great. I have found that he regularly (once or twice a year) gets random, often unexplained infections - skin rashes, eye infections, etc. So far, these have all just cleared up... usually without any treatment. While away at school, he did develop lots of respiratory infections... probably a combination of living with so many other students, not as healthy a diet, etc. (this has not been a problem since he finished school and moved back home). I'm sure remicade played a part but as it hasn't happened since he's moved back, I think the environment was more an issue with the respiratory infections.
I can understand your concerns re Covid-19. It is a worrisome time. I know it's difficult with teens but try to stress the importance of him doing all he can to help himself (mask, gloves, social distancing, etc.).. I know all this isn't much of a reassurance but it's a bit of a help.