"once contracted" is correct and usable in written English.
You can use it as an adverb to indicate that something happened in the past once and only once. For example: "I was once contracted to lecture at a local university."
My friend's options were at once contracted and enlarged.
There is no cure for polio once contracted; it can be prevented only by a series of vaccinations during childhood.
Though not as readily contagious as some other diseases, such as influenza, smallpox promises plenty of misery once contracted.
There is no human vaccine to prevent glanders, and once contracted, the disease is not always curable.
The works of Gabriel García Márquez contain a great deal of love, depicted as a doom, a demonic possession, a disease that, once contracted, cannot be easily cured.
Once contracted, genital herpes shows itself in the form of painful sores on the sex organs accompanied by fever and headaches.
Once contracts are signed, nothing can change.
Once contracts are established, they last for several years, giving providers financial security and the freedom to innovate.
The White House and the Federal Communications Commission say consumers should be free to unlock their phones once contracts are satisfied, Edward Wyatt writes in The New York Times.
Once contracts with arbitration clauses are signed, nursing homes can also use them to force civil cases involving sexual assault and wrongful death out of the courts.
The procurement rulebook will have to be redrafted once contracts no longer have to be advertised in the Official Journal of the European Communities.
