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

Rabies is almost always fatal once the initial symptoms appear, but it can be prevented through vaccination, effective surveillance and prompt access to post-exposure prophylaxis. — Nayara Batschke, Los Angeles Times, 15 Sep. 2026

Rabies post-exposure prophylaxis includes washing the wound in question, receiving the human rabies vaccine, and, if necessary, rabies immunoglobulins, according to the World Health Organization. — Ciara McCarthy, Fort Worth Star-Telegram, 14 Sep. 2026

The state health department said North Carolina has an adequate supply of prophylaxis and would provide it to anyone who needs it. — Jen Christensen, CNN Money, 4 Sep. 2026

Treatment after exposure to rabies, called post-exposure prophylaxis (PEP), consists of four to five rabies vaccine that must be administered as soon as possible. — Julia Gomez, USA Today, 3 Sep. 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