Health officials are still backing the safety of the vaccine to prevent the virus that causes most cases of cervical cancer. The Food & Drug Administration and the Centers for Disease Control & Prevention say Garadsil "continues to be safe and effective."

The statement from the two agencies goes on to say the benefits of the vaccine manufactured by Merck "continue to outweigh its risks."

Gardasil protects from four strains of the human papillomavirus, or HPV. The virus is commonly transmitted sexually and causes genital warts as well as most cases of cervical cancer.

Gardasil is one of Merck's top selling products, with more than 23-million doses distributed in the U.S. through the end of last year since its approval in 2006.

Writing in the "Journal of the American Medical Association," researchers say fainting and nausea among women receiving Gardasil is rare. Scientists say the vaccine does not seem to be causing unusual side effects.