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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These results support continued use of oseltamivir as the first-line treatment and for post-exposure prophylaxis in close contacts of infected individuals.
—
John Drake, Forbes.com, 27 Mar. 2025
But as antiretroviral exposure, ART during pregnancy, and pre-exposure prophylaxis (PrEP) reshaped the landscape, the Elton John AIDS Foundation demonstrated agility and shifted its focus to prevention and systemic change.
—Jeetendr Sehdev, Forbes, 26 Feb. 2025
People who are exposed to HIV have only 72 hours—less than the amount of time many clinics have now been closed—to begin a medication regimen called post-exposure prophylaxis that can help prevent infection.
—Hana Kiros, The Atlantic, 5 Feb. 2025
Even though deaths are rare – fewer than 10 people a year die from rabies in the US – about 60,000 people receive post-exposure prophylaxis after rabies exposure each year.
—Carma Hassan, CNN, 3 Dec. 2024
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John Drake, Forbes.com, 27 Mar. 2025
But as antiretroviral exposure, ART during pregnancy, and pre-exposure prophylaxis (PrEP) reshaped the landscape, the Elton John AIDS Foundation demonstrated agility and shifted its focus to prevention and systemic change.
—Jeetendr Sehdev, Forbes, 26 Feb. 2025
People who are exposed to HIV have only 72 hours—less than the amount of time many clinics have now been closed—to begin a medication regimen called post-exposure prophylaxis that can help prevent infection.
—Hana Kiros, The Atlantic, 5 Feb. 2025
Even though deaths are rare – fewer than 10 people a year die from rabies in the US – about 60,000 people receive post-exposure prophylaxis after rabies exposure each year.
—Carma Hassan, CNN, 3 Dec. 2024
See All Example Sentences for prophylaxis
Cite this Entry
“Prophylaxis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/prophylaxis. Accessed 12 Apr. 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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