At the time I thought it was odd to have me take the famotidine with the other meds but this might explain why.
I have a “Selective IgA Deficiency.” My immunologist recommended an H1 antagonist / blocker (Loratadine [Claritin]) AND an H2 antagonist / blocker (famotidine (Famotidine [Pepcid]) the day before my COVID vax, the day of, and the day after. I also kept an epipen on hand. This was for allergic reactions to the vax or the delivery chemicals.