Welcome @salmountain, My PMR has been in remission for 5+ years so I don't have any experience to share re: Covid booster or flu shot while being on prednisone. While we wait for members with experience, I thought I would share this information on the topic that might be helpful:

"Can I have the vaccine if I am taking steroids?
It’s fine for you to have the vaccine while you’re taking steroids. There’s no reason to delay the vaccine if you’re taking steroids, or have recently had a steroid injection or finished a course of steroid treatment.

Taking steroids as tablets, liquids, injections or drips might mean that your immune system doesn’t respond as well to the vaccine as someone who isn’t taking these drugs. This means that you may be advised to follow advice on shielding and social distancing guidance after you have had it and if you may need a third dose of the vaccine as part of your initial course. Steroid creams or eye drops should not affect your immune system or response to the vaccine.

Your healthcare team might want to discuss delaying a dose of steroids or a steroid injection with you, especially if there is a high risk of getting COVID-19. It’s important that you don’t stop taking your steroid medication without speaking to a healthcare professional, as this can leave you at risk of having a flare-up, which can increase your risk of COVID-19."
--- Vaccines for COVID-19 – your questions answered: https://versusarthritis.org/covid-19-updates/vaccines-for-covid-19-your-questions-answered/.

There is another discussion you might find helpful:
--- PMR Dosages and Managing Symptoms: https://connect.mayoclinic.org/discussion/pmr-dosages/.

One of the things that I found helpful that was recommended by my rheumatologist was to keep a daily log of my level of pain when waking up in the morning along with that days dose of prednisone. Even on good days I normally had a 1 or 2 level of aches/pain when waking up.
Do you keep a daily log?

Hello salountain,
I am 79, Stil a practicing massage therapist. Been on prednisone for about 7 months. I have had both the flu shot, and the latest covid vaccine. due to the far number ov f cases

For anyone considering vaccines, I will share my story in case anyone finds it helpful...I have had PMR for 5.5 years (started at age 57, starting well before covid existed). I have been on prednisone at various doses and have had multiple flares. I have never gotten below 2.5 mg without a flare. I probably have a genetic predisposition as my grandmother had PMR/GCA and my mother has PMR. I am currently on prednisone 5 mg daily and am trying Methotrexate 10 mg weekly to see if it helps reduce PMR flares and possibly wean off prednisone. I recently decided to get the latest COVID vaccine, flu vaccine, and RSV vaccines all at once. Some research has shown higher antibody titers after covid vax among patients who skipped 10 days to 2 weeks of methotrexate, so I skipped one dose (although my rheumatologist did not think skipping a dose was necessary.) I experienced vaccine side effects for 24-48 hours: fever/chills, soreness, and fatigue. This was very similar to all my prior flu or covid vaccine responses. While I know that some may have experienced PMR symptoms following covid vaccines, this has not happened to me. PMR may be triggered by any virus or challenge to the body and has existed long before vaccines, covid or otherwise. I am feeling just fine now. Hopefully this will reduce my risk of RSV/flu/covid. Best to all!

I was diagnosed in January of this year. After being off prednisone for 5 weeks yesterday. The 5 day flare-up that I had was so painful that I saw Doc yesterday. I am now back on prednisone for a 14 week taper to Kezvara starting with 20mg for 2 weeks, but first he gave my wife and I Covid booster and flu. Went home and started back on prednisone. Today, after a dose yesterday and this morning I am at 95% no pain or stiffness. You love and hate prednisone at the same time. If you are now on prednisone check with Doc before you get the vaccine.
Good luck