Tetanus vaccines are available as sole ingredient. The thinking is now that once every 3 years is good enough. Years ago I questioned my vet as to why it was recommended annually when human recommendations were every 10 years. She replied that the research was conducted by the manufacturers of the products. Yeah! right as always FOLLOW THE MONEY. 
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- Frances C.
December 2017, Washington & California
Case history: https://ecir.groups.io/g/CaseHistory/files/Frances%20and%20Phoenix
Phoenix's Photo Album: https://ecir.groups.io/g/CaseHistory/album?id=12382