I have been waiting for someone to look at this. People with connective tissue problems are like canaries in the coal mine. I have hEDS and was devastated by the vaccine. Reactivated viruses and lyme, severe headaches and joint pain, POTS, MCAS, high liver enzymes and myopericarditis. I am lucky to have survived it all.
Here’s a ME/CFS study looking at the genetics of pwME. If hypermobility / hyperflexibility is due to Ehlers-Danlos Syndrome caused by genetics, that certainly wasn’t found in this genetics study (using genome-wide association). I haven’t checked how many of the EDS genes were examined in the GWAS.
This suggests that hypermobility is an environmental factor, presumably picked up very early in life such as mother → child transmission of an infectious agent. It seems like a risk factor for chronic illness.