side effect

noun

Definition of side effect

: a secondary and usually adverse effect (as of a drug) toxic side effects

called also side reaction

Examples of side effect in a Sentence

Nausea and diarrhea are the side effects of the drug. the harmful side effects of using chemicals to kill insects The merger created positive side effects for both companies.
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Recent Examples on the Web The Johnson & Johnson vaccine, which was briefly paused while health officials investigated a very rare side effect, requires just one shot. Elizabeth Weise, USA TODAY, "About 92% of Americans got their second COVID shot. That's better than most two-dose vaccines but experts say the rest should do it now.," 29 Apr. 2021 The government briefly paused administration of the Johnson & Johnson vaccine to study a rare but dangerous side effect occurring in younger women. Nr Editors, National Review, "The Week," 29 Apr. 2021 Vaccine distribution for Johnson & Johnson was paused this month after it was linked to a rare and severe side effect that caused blood clots in 15 individuals out of 6.8 million people who received the vaccine. Elizabeth Gamillo, Smithsonian Magazine, "CDC Data Shows That 92% of Partially Vaccinated Americans Are Returning for Their Second Dose," 27 Apr. 2021 The use of that vaccine, made by Johnson & Johnson, was paused this month after it was linked to a very rare but serious side effect involving blood clotting. New York Times, "Millions Are Skipping Their Second Doses of Covid Vaccines," 25 Apr. 2021 The use of that vaccine, made by Johnson & Johnson, was paused this month after it was linked to a very rare but serious side effect involving blood clotting. BostonGlobe.com, "Millions of people are skipping their second doses of COVID vaccines," 25 Apr. 2021 But there should be a fact sheet that provides the information to everybody to understand what the nature is of this potential very rare side effect so that everyone is aware of the facts. NBC News, "Meet the Press - April 25, 2021," 25 Apr. 2021 Overall, the committee decided the benefits of the Johnson & Johnson vaccine still outweigh the chance of this very rare side effect. Kristen Jordan Shamus, Detroit Free Press, "Michigan to resume use of Johnson & Johnson COVID-19 vaccine after safety review," 24 Apr. 2021 The pause on the Johnson & Johnson vaccine came after six cases in which recipients suffered from a rare side effect– the blood clot cerebral venous sinus thrombosis. Ashlee Banks, Essence, "CDC Votes to Resume Johnson & Johnson Vaccine," 23 Apr. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'side effect.' 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 side effect

1814, in the meaning defined above

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Time Traveler for side effect

Time Traveler

The first known use of side effect was in 1814

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Statistics for side effect

Last Updated

1 May 2021

Cite this Entry

“Side effect.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/side%20effect. Accessed 8 May. 2021.

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More Definitions for side effect

side effect

noun

English Language Learners Definition of side effect

: an often harmful and unwanted effect of a drug or chemical that occurs along with the desired effect
: a result of an action that is not expected or intended

side effect

noun

Medical Definition of side effect

: a secondary and usually adverse effect (as of a drug) toxic side effects a side effect of drowsiness caused by antihistamines

called also side reaction

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Comments on side effect

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