pro·​phy·​lax·​is | \ ˌprō-fə-ˈlak-səs also ˌprä- How to pronounce prophylaxis (audio) \
plural prophylaxes\ ˌprō-​fə-​ˈlak-​ˌsēz How to pronounce prophylaxes (audio) also  ˌprä-​ \

Definition of prophylaxis

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

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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

While not all exposures require treatment, those that do receive what’s known as postexposure prophylaxis, a regiment of five injections over a 13-day period. Leada Gore |,, "Bats close Alabama daycare; officials recommend children receive rabies treatment," 1 July 2019 The approach is called PrEP, or preexposure prophylaxis. NBC News, "Daily HIV prevention pill urged for healthy people at risk, new guidelines say," 11 June 2019 All employees have been treated with post-exposure prophylaxis and returned to work, the health department said. Aimee Picchi, CBS News, "On National Doughnut Day, some Dunkin' Donuts customers warned of hepatitis A infection," 7 June 2019 Rabies post-exposure prophylaxis is generally recommended for individuals who have a possible exposure to the virus. Tara C. Smith, SELF, "What Happens When You Get Rabies? An Epidemiologist Explains," 24 Jan. 2019 Depending on the situation at hand, your doctor may decide to administer what’s called a prophylaxis against Lyme disease, Luis Marcos, M.D., the fellowship program director at Stony Brook Medicine’s division of infectious diseases, tells SELF. Kate Sheridan, SELF, "Here’s Exactly What to Do if a Tick Bites You," 14 July 2018 Aureomycin spawned a class of antibiotics called the tetracyclines still used for everything from soft tissue infections to malaria prophylaxis. Aaron Gilbreath, Longreads, "We Are Scientists," 5 June 2018 Wash any wounds with soap and water to decrease the chance of infection, and see a doctor before considering the need for a rabies vaccination, known as postexposure prophylaxis. Brittany Britto,, "Explainer: On groundhogs, rabies and what we know (and don't know) about Carroll's rodents," 9 May 2018 The Food and Drug Administration administered guidelines that prohibit antibiotic use for growth promotion, but continue to allow the routine use of antibiotics on animals that aren’t sick for prophylaxis. Matthew Wellington, STAT, "Lawmakers must act on limiting antibiotic use in food animals," 19 Mar. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'prophylaxis.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of prophylaxis

1683, in the meaning defined above

History and Etymology for prophylaxis

New Latin, from Greek prophylaktikos

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Statistics for prophylaxis

Last Updated

7 Jul 2019

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Time Traveler for prophylaxis

The first known use of prophylaxis was in 1683

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More Definitions for prophylaxis


pro·​phy·​lax·​is | \ -ˈlak-səs How to pronounce prophylaxis (audio) \
plural prophylaxes\ -​ˈlak-​ˌsēz How to pronounce prophylaxes (audio) \

Medical Definition of prophylaxis

: 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

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More from Merriam-Webster on prophylaxis

Rhyming Dictionary: Words that rhyme with prophylaxis

Britannica English: Translation of prophylaxis for Arabic Speakers Encyclopedia article about prophylaxis

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