I've had both ... the Moderna. On the second was I felt a little chills ... achy.

I once had an echo done and EF was read at 28% so I was sent to the cath lab the next day. Guess what? My EF was really 50-55%. The echo was mis-read. I was upset at the cardiologist that read the echo and made me go through having a cath, although I was so relieved to hear that I was fine. I had already had my mitral valve replaced twice, so wasn't looking to having a low EF. If you have two different EF readings, one of them is wrong.I wish you the best.

If it persists perhaps let your G.P. know...also maybe your cardeologisr...