I checked with Kaiser, this is a legitimate Kaiser phone #. But I agree, you really have no way of knowing whether it's legit or not when you call because it's a recording that starts asking your personal info (to verify your ID).

Very suspicious voicemail. A woman's voice states-information for her, please pass along and have call 855-610-9291. I believe this is some type of scam and did not call back.

Said it was Kaiser but the area code was weird. The woman though sounded very "Kaiser-like" but I'm not calling back. Could be one of those scams that if you call back, you'll be charged some fee on your phone automatically.

I got it too. Voice mail said it's from Kaiser Permanente and has important information to share.  I checked Kaiser, they do not have such a number. When I called back, a machine asked my phone number. This is likely a fake Kaiser call for personal information.