Merck issued a voluntary recall of a lot of its Gardasil vaccines Friday due to the risk that some of the viles may contain glass particles, according to a company statement.
The company estimates that only 10 of the 743,360 vials in the lot may have been affected. The vaccines were distributed between August 20, 2013 and October 9, 2013 in the United States and Puerto Rico.
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A medical assessment conducted by Merck concluded that if a vaccine containing glass particles is administered to a patient, there is a remote risk of an injection site reaction.
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Gardasil protects against certain strains of human papillomavirus (HPV), which can cause cervical cancer in women. The Center for Disease Control and Prevention recommends HPV vaccination of boys and girls ages 11 and 12, though it is approved to be given to people ages 9 to 26.
Shares of Merck were largely unchanged in the wake of the news.
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—By CNBC's JeeYeon Park. Follow her on Twitter @JeeYeonParkCNBC.