which vaccines does my cat need and when

Which vaccines you cat needs depends on which diseases kitty is realistically likely to be exposed to and how dangerous they are, which in some cases depends on how old kitty is.

For example, protection against feline leukemia is important for kittens who have a risk of exposure, but adult cats with healthy immune sstems develop a natural immunity to it (and if they don't have a healthy immune system, vaccinating them probably wouldn't work.)

There are other diseases that are life threatening to kittens but merely annoying to adults.

Also, most (probably all) vaccines will protect kitty for much longer than the USDA certifies them for.

It's important to keep vaccinations to a minimum because of the risk of Vaccine-Associated Sarcomas, nasty and tenacious cancers (usually fibrosarcoma) triggered by the inflammation produced as part of the vaccination process. Although there have been many long term VAS survivors (my late great Rusty was one) most cats afflicted with VAS die from it, usually sooner rather than later. For those who survive (and for many who don't) the cost of treatment can be several thousand dollars or more.

Along with limiting the number and frequency of vaccinations as much as possible, you should seek out the safest products. Research results conflict on this, but most oncologists believe that non-adjuvenated vaccines are less likely to trigger VAS because they produce less inflammation. Oncologists also generally agree that the new recombinant DNA vaccines (Meriel's Purevax) are even less likely to trigger VAS, although there are enough Purevax-triggered VAS cases to prove that it isn't 100% VAS-safe.