My Wife Got The Flu Shot Yesterday. This Evening We

My wife got the flu shot yesterday. This evening we were sitting on the couch and I noticed a swollen left supraclavicular node that she hadn't noticed herself so obviously it had not been hurting. After I palpated it she said it was painful. She woke up this morning with a fever and sore throat feeling like a truck hit her. She was really weak as well. Naturally worrying about the possibility of cancer, how likely is it that this from the flu shot?