shared vent

Is it OK for the shower to be on the same vertical drain/vent line as the toilet? Seems risky, if toilet clogs. Could back up into shower. But I can't figure out any other way to vent the shower. The shower line is the 2" blue one. The toilet stack is 3". My apologies if this is a...

I have been reading about plumbing codes and methods on this site for many years and I learned a lot but I still don't know everything so I must ask a question. I have removed all the cast iron DWV parts so everything will be PVC. I am also installing a full bathroom and seperate floor drain...