It most certainly is unpleasant, for the parent and for the child. One thing that helps is to keep it mind what the alternative is - having your child actually getting the disease.

One of my middle school classmates (from India) had leg deformities from polio, and could not walk without the help of crutches. He couldn't participate in most school activities, and was teased often. I wasn't able to find out why he wasn't vaccinated, but he was from a wealthy family so we always assumed they were in the anti-vaccination camp. Can you imagine being in his place? He has to suffer for his entire life because of a dumb decision that his parents made.

BTW I realize that polio vaccination does not require painful injections, but just pointing out that there are severe downsides to not vaccinating your child. Most certainly severe than a few jabs.