pro·​phy·​lax·​is | \ ˌprō-fə-ˈlak-səs How to pronounce prophylaxis (audio) also ˌprä- \
plural prophylaxes\ ˌprō-​fə-​ˈlak-​ˌsēz How to pronounce prophylaxis (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 There are other strategies that can also reduce HIV transmission risk, like condom use and taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP), two medications that lower your risk of contracting the virus. Mathew Rodriguez, SELF, "Jonathan Van Ness on Vulnerability Hangovers, Dating With Intention, and Living With HIV in a Pandemic," 1 Dec. 2020 The White House staff knew Boulware had been working on post-exposure prophylaxis, and the president's doctor wanted to see the trial results. Adam Rogers, Wired, "The Strange and Twisted Tale of Hydroxychloroquine," 11 Nov. 2020 Cheaper and quicker tests are already becoming available, and fairly soon there may be antibody and other treatments which, given early, reduce the risk of severe disease, and which might even offer some degree of prophylaxis. The Economist, "The second wave of covid-19 has sent much of Europe back into lockdown," 7 Nov. 2020 But the number of doses will initially be limited, and choosing to use antibodies for prophylaxis over treatment may be frowned upon by medical ethicists. New York Times, "A Dose of Optimism, as the Pandemic Rages On," 12 Oct. 2020 Open-air prophylaxis was available to paying clients at a sanatorium, but not the families of workers or the poor. Daniela Blei, Smithsonian Magazine, "When Tuberculosis Struck the World, Schools Went Outside," 1 Sep. 2020 Trump spent weeks pushing the drug as a potential cure or prophylaxis for COVID-19 against the cautionary advice of many of his administration’s top medical professionals. Darlene Superville, The Denver Post, "Trump says he’s taking malaria drug hydroxychloroquine in case he gets coronavirus," 18 May 2020 Pre-exposure prophylaxis, or PrEP, is a drug typically taken once daily in pill form with the guidance of a doctor to prevent contracting HIV. Jeanine Santucci, USA TODAY, "Trump praises scientists for nonexistent AIDS vaccine, predicts COVID-19 vaccine by the end of 2020," 17 June 2020 According to Science magazine, a Spanish study on post-exposure prophylaxis involving 2,300 people also found no benefit of hydroxychloroquine. Beth Mole, Ars Technica, "WHO gives up on hydroxychloroquine for COVID-19, stops trials," 17 June 2020

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

3 Dec 2020

Cite this Entry

“Prophylaxis.” Dictionary, Merriam-Webster, Accessed 25 Jan. 2021.

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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 prophylaxis (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

More from Merriam-Webster on prophylaxis

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

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