protect backups from ransomware

i work for a hospital and there are quite a few hospitals that have been attacked by ransomware. In some of these attacks , they encrypted the live data as well as the backups.  I am wondering how protected is our backups that reside on the MSDP pool .  We have both appliances as well as regular servers configured with dedup pool.

what are the chances of these being encrypted by the ransomware itself

if anyone has taken steps to protect against such attacks , it would be great if you can share those.

Thanks