When you create a recipient by default they are made public. As an owner you can elect to make the recipient private. By doing this only the owner can manage the sharing permissions of the recipient and send them communications.
Navigate to the Recipients page
Select the recipient
Scroll to Recipient Sharing
Select the pencil (edit) icon
Turn the public toggle off (toggle will turn grey)
An owner has the ability to share recipients with another user or group. If shared with other users, those users can view the recipient information and send them communications.