Merck has rejected claims by Republican US presidential candidate Michele Bachmann that human papilloma virus (HPV) vaccine Gardasil could cause mental retardation in children.

Bachmann yesterday criticised Texas Governor Rick Perry – whom she is running against for the Republican nomination – for making an executive order four years ago requiring girls in the state to be vaccinated against HPV, which can lead to cervical and vulva cancer.

She told the Today programme, “I had a mother last night come up to me here in Florida after the debate. She told me that her little daughter took that vaccine, that injection, and she suffered from mental retardation thereafter. It can have very dangerous side effects.”

Merck responded in a statement, “The efficacy and safety of Gardasil was established in clinical trials in thousands of patients. Since its approval in 2006, the vaccine has been given to millions of girls around the world. Merck remains strongly committed to preventing cervical cancer.”

Last month, the Institute of Medicine reaffirmed the safety of a number of vaccines, including HPV vaccines, and concluded, “Despite much media attention and strong opinions from many quarters, vaccines remain one of the greatest tools in the public health arsenal.”

Gardasil is approved for use in girls and young women aged nine to 26 for the prevention of cervical, vulvar, vaginal and anal cancers caused by HPV types 16 and 18; genital warts caused by HPV types 6 and 11; and precancerous or dysplastic lesions caused by HPV types 6, 11, 16 and 18.