The neulasta injection os to help your white cells recover faster, as chemo can cause them to drop dangeruosly low, a condition called neutropaenia. You will get lots of information about what to do if you develop a temperature whilst going through chemo, from the chemo nurses.
Some places give all patients having certain chemo combinations the injections. Where I had my chemo you only got it if you had an episode of febrile neutropaenia, so a high fever combined with a low white cell count.
This cancer thing is a s teep learning curve.
At the time I was working in a gp practice. I didn't catch anything, worked 3 days a week right through other than one week off when I did have febrile neutropaenia, never found a cause for the fever, though