I'd rather get the flu than to ever suffer the ill-effects from the flu shot ever again. I did ask my Dr. about the nasal vaccine, but he said there are side effects to that, too. So, I think I'll take my chances & trust my own immune system from now on.
As to my rehab, the PT guy said that if there was no improvement, he would have suggested the MRI to find out what's actually going on. I did the exercises every day (with heat before, ice after), and I didn't need the MRI. I'm still having some discomfort when I reach a certain way, but I have mobility & functionality again. I keep doing my daily PT exercises, too.
Two Physical Therapists also said that frozen shoulder is very common for women between age 35 - 40s (they don't know why). And there is a new line of thinking that if Nothing is done, it may resolve itself in 2 - 3 years. I didn't want to be with that kind of pain or uncertainty. I worked out the payment arrangements & got the PT sooner rather than later.
Good luck to you!