Parents should have children vaccinated against human papilloma virus because it causes more cancers than anything besides smoking, U.S. researchers say.Thomas Melendy, an associate professor at the University at Buffalo School of Medicine and Biomedical Sciences, and colleagues are working to develop an antiviral drug against HPV infections, as well as strategies that would kill HPV cancer cells while leaving normal cells alone.Melendy said HPV has co-evolved with humans over millions of years and are very common -- and almost everyone has one at some point in their lives.Most infections create a small benign wart, which is generally resolved by our immune systems. Some strains only infect the outer skin while others are sexually transmitted and only infect the genitalia.About one out of nine people in the United States have an active HPV sexually transmitted infection at any time. Some require treatment while others may not be apparent and resolve on their own.HPV causes cervical cancer, the third-most common cancer in U.S. women, and it causes almost all other anogenital -- anus and the genitals -- cancers and more than half of oral cancers.Unlike other cancers, such as breast cancer, the absence of a family history of cervical cancer provides little statistical protection.Regular Pap smears help catch cervical cancer early, so it\'s more treatable, but nearly one in three cases still results in death in the United States, or approximately 5,000 deaths a year, Melendy said.