I've been a pedi nurse for almost 3 yrs. I follow that same kind of system. Also remember that any vax with tetorifice in it (dtap, tdap) is painful as well. I usually put the more painful vax in the pt's nondominant hand (if they are fine with that). Another key point is to always try and split up the vaccines (one in R arm, one in L arm) if there are two. Certain age groups may need one in each extremity! Also, do the less painful one first! I learned that the following vaccines are "more painful": HPV, PCV13, tdap/dtap, mmr, varivax. Hope this helps :)