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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People who have been exposed are advised to get post-exposure prophylaxis, which includes a dose of human rabies immune globulin (HRIG) and a four-dose series of rabies vaccine.
—
Beth Mole, ArsTechnica, 13 Aug. 2025
Doctors will typically prescribe a post-exposure prophylaxis (PEP) with a 200-milligram dose of the antibiotic doxycycline to be taken within 72 hours of a high-risk tick bite, epidemiologists told Fox News Digital.
—Amy McGorry, FOXNews.com, 29 July 2025
In addition to such highly effective barrier methods of prevention, there are newer medicines—like pre-exposure prophylaxis, or PrEP, and PEP for post-exposure protection.
—Victoria Uwumarogie, Essence, 21 July 2025
Post-exposure prophylaxis is offering someone a drug or vaccine after they are exposed to a germ, to reduce the chance they will be infected or develop severe disease.
—Sarah Lynch Baldwin, CBS News, 17 June 2025
See All Example Sentences for prophylaxis
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Beth Mole, ArsTechnica, 13 Aug. 2025
Doctors will typically prescribe a post-exposure prophylaxis (PEP) with a 200-milligram dose of the antibiotic doxycycline to be taken within 72 hours of a high-risk tick bite, epidemiologists told Fox News Digital.
—Amy McGorry, FOXNews.com, 29 July 2025
In addition to such highly effective barrier methods of prevention, there are newer medicines—like pre-exposure prophylaxis, or PrEP, and PEP for post-exposure protection.
—Victoria Uwumarogie, Essence, 21 July 2025
Post-exposure prophylaxis is offering someone a drug or vaccine after they are exposed to a germ, to reduce the chance they will be infected or develop severe disease.
—Sarah Lynch Baldwin, CBS News, 17 June 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 23 Aug. 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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