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 This fall Governor Gavin Newsom signed legislation to make PrEP (post-exposure prophylaxis), which can be taken daily to prevent HIV, available to Californians over the counter. Tanya A. Christian, Essence, "Regal Black Statue Unveiled In Former Capital Of The Confederacy + 9 Other Headlines We're Talking About," 18 Dec. 2019 Advocates of Senate Bill 159 say California is the first state to authorize pre-exposure prophylaxis (PrEP), and post-exposure prophylaxis (PEP), without prescriptions. Fox News, "California allows patients to buy HIV prevention meds without prescription," 8 Oct. 2019 The medications covered by the new legislation are pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP), which both help prevent HIV infections. Joe Sutton, CNN, "HIV-prevention drugs will soon be available without a prescription at California pharmacies," 8 Oct. 2019 One is that after Truvada received approval from the U.S. Food and Drug Administration (FDA) in 2004 as a treatment for HIV infection, CDC guidelines endorsed it for PrEP’s close cousin, post-exposure prophylaxis, or PEP. Jon Cohen, Science | AAAS, "Untangling the Trump administration’s lawsuit over an HIV prevention drug," 8 Nov. 2019 The government first applied for patents on prophylaxis techniques in 2006. New York Times, "Who Owns H.I.V.-Prevention Drugs? The Taxpayers, U.S. Says," 8 Nov. 2019 Published materials clearly show that, well before HHS claims to have invented the concepts of PrEP and PEP in 2006, others had conceived of using an antiretroviral therapy, including Truvada, for both forms of prophylaxis. Ed Silverman, STAT, "HHS sues Gilead for refusing to reach a licensing deal over patents for HIV prevention pills," 7 Nov. 2019 Advocates of Senate Bill 159 say California is the first state to authorize pre-exposure prophylaxis, also called PrEP, and post-exposure prophylaxis, known as PEP, without prescriptions. San Diego Union-Tribune, "California OKs pharmacists to dispense HIV prevention meds," 7 Oct. 2019 According to park officials, rabies is preventable if medical treatment called post-exposure prophylaxis, or PEP, is given following a person's exposure to a rabid animal. Mike Cruz, azcentral, "2 dead bats from Grand Canyon National Park test positive for rabies," 14 Sep. 2019

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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Time Traveler for prophylaxis

Time Traveler

The first known use of prophylaxis was in 1683

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Statistics for prophylaxis

Last Updated

22 Dec 2019

Cite this Entry

“Prophylaxis.” The Dictionary, Merriam-Webster Inc., Accessed 18 January 2020.

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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

Comments on prophylaxis

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