How much was I at fault for my cat's death?

I took my 14-1/2-year old cat (my absolute favorite cat) in for her booster shots. Exactly one week later I had to have her put to sleep because her kidneys were failing. I feel now that I shouldn't have given her the shots because she rarely went outside, and when she did, she only laid in the sun in the driveway. I think the chemicals were too much for her. Do you think her kidneys were starting to fail anyway, and the shots just hastened the inevitable?