prophylaxis

noun

pro·​phy·​lax·​is ˌprō-fə-ˈlak-səs 

also ˌprä-

plural prophylaxes ˌprō-fə-ˈlak-ˌsēz 

also ˌprä-

: measures designed to preserve health (as of an individual or of society) and prevent the spread of disease

Did you know?

In Greek, phylax means "guard", so prophylactic measures guard against disease by taking action ahead of time. Thus, for example, before the polio vaccine became available, prophylaxis against polio included avoiding crowds and public swimming pools. These days a well-known kind of prophylactic is used to prevent sexually transmitted diseases; but prophylactic measures only work when people use them.

Examples of prophylaxis in a Sentence

Recent Examples on the Web

Gilead officials say that’s similar to some other types of PrEP, which stands for pre-exposure prophylaxis. — ABC News, 2 Nov. 2026

Medication called post-exposure prophylaxis (PEP) may prevent infection if started within 72 hours, preferably sooner. — Md Published, Verywell Health, 23 Oct. 2026

PrEP, which stands for pre-exposure prophylaxis, helps prevent HIV-infection after an individual is exposed to the virus. — Erin Wisti, Footwear News, 11 Oct. 2026

Four people were also possibly exposed and were receiving follow-up for rabies post-exposure prophylaxis. — Dean Fioresi, CBS News, 6 Oct. 2026

Word History

Etymology

borrowed from New Latin, from Greek prophylak-, stem of prophylássein "to keep guard before a place, be on guard, (middle voice) to be on one's guard against, take precautions against" (from pro- pro- entry 1 + phylássein "to keep watch on, guard, preserve," derivative of phylak-, phýlax "guard, guardian, protector") + -sis -sis — more at phylactery

First Known Use

1683, in the meaning defined above

Phrases Containing prophylaxis

• post-exposure prophylaxis
• preexposure prophylaxis

Rhymes for prophylaxis

• chemotaxis
• epistaxis
• anaphylaxis
• axis
• praxis
• taxus
• chemoprophylaxis

Medical Definition

prophylaxis

noun

pro·​phy·​lax·​is -ˈlak-səs 

plural prophylaxes -ˈlak-ˌsēz 

: measures designed to preserve health and prevent the spread of disease : protective or preventive treatment

prophylaxis against viral diseases

a paste containing fluorine for dental prophylaxis