It seems that hospitals need not be members of the MS-ISAC to get services like the MDBR service (Malicious Domain Blocking and Reporting Service) for free.

Here is the Washington Post article:
https://www.washingtonpost.com/politics/2021/03/02/cybersecurity-202-nonprofit-is-providing-free-ransomware-protection-private-us-hospitals/?utm_campaign=wp_the_cybersecurity_202&utm_medium=email&utm_source=newsletter&wpisrc=nl_cybersecurity202