Anyone 30+ remember hearing of friends/family getting hand/foot/mouth disease when we were kids?

Here is scientific research about the connection between HFMD & Polio for your reference:

Exploring the Link between Polio Vaccination and Hand Foot Mouth Disease

http://epivax.com/news/exploring-the-link-between-polio-vaccination-and-hand-foot-mouth-disease

Hand, foot, and mouth disease: current scenario and Indian perspective.

https://www.ncbi.nlm.nih.gov/m/pubmed/23442455/

Coxsackievirus: https://en.m.wikipedia.org/wiki/Coxsackievirus

Is Hand, Foot, and Mouth Disease Really a Big Deal?

https://www.livingwhole.org/hand-foot-mouth-disease-really-big-deal/

[An investigation on a case of hand-foot-mouth disease caused by coxsackie-virus A6 associated with a vaccine-derived poliovirus co-infection].

https://www.ncbi.nlm.nih.gov/m/pubmed/24685040/

Polio, Foot and Mouth Disease, and Hepatitis A: The Picornaviridae Virus Family

https://study.com/academy/lesson/polio-foot-and-mouth-disease-and-hepatitis-a-the-picornaviridae-virus-family.html

Non-Polio Enteroviruses

https://www.cdc.gov/non-polio-enterovirus/outbreaks-surveillance.html