Unfortunately there will be no significant herd immunity effect to protect the immunocompromised. They will all be exposed.

The main benefit of vaccines is in reducing symptom severity. They only produce a limited and temporary reduction in transmission risk.

https://www.medpagetoday.com/opinion/vinay-prasad/94646

https://www.nature.com/articles/d41586-021-02689-y

https://www.businessinsider.com/delta-variant-made-herd-immu...