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
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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
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The Task Force is in charge of recommending preventive healthcare services and technologies that ought to be covered by insurers, such as cancer screenings, cholesterol medications and HIV prevention drugs or pre-exposure prophylaxis, at no cost to patients.
—
Joshua P. Cohen, Forbes.com, 7 July 2025
Friday's case arose when the preventive care task force classified pre-exposure prophylaxis (PrEP) drugs as essential to preventing HIV.
—Nina Totenberg, NPR, 27 June 2025
For nearly twelve years, Gilead had been selling a pill named Truvada as a preventive treatment called pre-exposure prophylaxis, or PrEP.
—Jon Cohen, New Yorker, 24 June 2025
This method of receiving antibiotics after exposure, known as post-exposure prophylaxis, can help reduce their chance of contracting pertussis.
—Katia Hetter, CNN Money, 1 May 2025
See All Example Sentences for prophylaxis
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Joshua P. Cohen, Forbes.com, 7 July 2025
Friday's case arose when the preventive care task force classified pre-exposure prophylaxis (PrEP) drugs as essential to preventing HIV.
—Nina Totenberg, NPR, 27 June 2025
For nearly twelve years, Gilead had been selling a pill named Truvada as a preventive treatment called pre-exposure prophylaxis, or PrEP.
—Jon Cohen, New Yorker, 24 June 2025
This method of receiving antibiotics after exposure, known as post-exposure prophylaxis, can help reduce their chance of contracting pertussis.
—Katia Hetter, CNN Money, 1 May 2025
See All Example Sentences for prophylaxis
Cite this Entry
“Prophylaxis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/prophylaxis. Accessed 29 Jul. 2025.
Copy CitationMedical 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
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