The full article says that the chemical approved as an "adjuvant" (something that boosts the pharmacological effects of the vaccine) in the US for vaccines is aluminum hydroxide, or alum.
"It can boost immunity, but also trigger fever and other side effects. One obstacle blocking vaccine improvements is that researchers didn't know how alum tweaks the immune system. But some recent studies suggest that alum provokes the inflammasome. If so, researchers might be able to fine-tune adjuvants to induce a strong inflammasome response while provoking fewer side effects."
It seems like they haven't figured out whether this adjuvant, in the vaccine, is good or bad for Crohn's.