The best replacement for titer is titre.

The best alternatives to titer are rated as following:
★★★★★  titre
★★★★  vaccine
★★  booster
★★  vaccination
★★  antibody
★  immunization
  low titer
  igm titer
  high titer
  varicella

Your alternative for titer is not listed? Suggest!
Speaking about titer, one probably shouldn't forget about reflex.

Other search terms related to titer and their ratings are:
★★★★★ reflex
★★ mpo/pr3
You have in mind a companion for titer and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of titer in all years. Click on graph for more.
titer
titre
vaccine