Covid Vaccine Payment for out of network insurance

We have been administering Covid vaccine to people who meet criteria per CDPH and CDC.

I am surprised to learn that some teachers who have PPO insurance received the Covid vaccine elsewhere and only their coworkers who have Medicaid and HMO are coming to my office for Covid vaccines.

Is there something in writing that states that regardless of whether I am in network the Covid vaccine administration will be covered at my office?

I just received the temporary authorization to bill Medicare and wonder if I also have to enroll “temporarily” in all the Medicaid and HMOs in order to receive the minimal payment for vaccine administration from the insurance companies.

Thank you