Study finds that one dose of HPV vaccine that targets only cervical cancer is as effective as three doses, now recommended

By Melissa Patrick
Kentucky Health News

A study has found that one dose of the human papillomavirus vaccine Cervarix appears to be as effective in preventing HPV infections that lead to cervical cancer as do three doses, the recommended course of vaccination. Only 25 percent of Kentucky adolescent women initiate the vaccination, and fewer than one in nine of those who do get three does, according to the Kentucky Cancer Consortium.

“Many women around the world and in the U.S. don’t get the full three doses that are recommended, so this is promising news,” said Elisia Cohen, an associate professor of communication at the University of Kentucky, who does extensive research on community strategies to improve adolescent and adult vaccinations. However, she cautioned that the drug Cervarix is “only 1 percent of the U.S. market” and that the findings from this study do not apply to Gardasil, the drug most commonly used in the U.S.

Dr. Diane Harper of the University of Louisville, one of the researchers, said in a news release, “Kentucky is one of the states that has not had a program in place to make Cervarix available to all of its citizens, and has very low three-dose completion rates of Gardasil.”

Most health departments and physicians choose Gardasil over Cervarix because it protects against four strains of HPV: two strains that cause 70 percent of all cervical cancers and two strains that cause genital warts and oral and anal cancers, concerns for males as well as females. Cervarix only protects against the two strains that cause cervical cancer. “Generally, the thinking is that protection against four strains is better that two,” Cohen said.

She said Gardasil 9, which will protect against 90 percent of HPV strains that cause cervical cancer as well as pre-invasive cervical cancer lesions, has just been approved by the U.S. Food and Drug Administration and is going through its labeling process, and will be recommended for both boys and girls.

HPV is the most common sexually transmitted infection in the U.S., affecting an estimated 79 million individuals, according to the federal Centers for Disease Control and Prevention.

The study, published in The Lancet Oncology, analyzed data from two large trials of Cervarix. In the trials, women were randomly chosen to receive three doses of Cervarix or a control vaccine. All of the women were evaluated, regardless of how many doses of the vaccine they received, for the effectiveness of the vaccine for a period of four years. The analysis found that the protection from one dose was similar to that achieved by three doses of the vaccine.

“Knowing that Cervarix offers protection in one dose reassures public health agencies that they are not wasting money when most of their vaccines are given to those who never complete the three-dose series,” the researchers wrote.

The CDC recommends HPV vaccination for girls 11 and 12 years old, and catch-up vaccination for females from 13 to 26. The second dose should be given one to two months after the first injection; the third dose should be administered six months after the first dose.

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