There are a variety of immune boosting products out there; examples include immunoplex and congaplex. If you look at the other major brands such as thorne, integrative thereaputics, pure encapsulations, seroyal, etc. you will see they have immune support products as well.
Also minerals are a great way to boost the immune system and specific ones work really well such as calcium, magnesium, and copper.
I could go on and on about this topic…