A single dose of the human papillomavirus (HPV) vaccine Cervarix appears to be as effective in preventing certain HPV infections as three doses, the currently recommended course of vaccination. That is the conclusion of a study published today in The Lancet Oncology and co-authored by Diane Harper, M.D., Ph.D., the Rowntree Endowed Chair and professor in the Department of Family and Geriatric Medicine at the University of Louisville School of Medicine.
In the study, data from two large trials of the vaccine Cervarix were analyzed to compare the effectiveness of one, two or three doses of the vaccine in preventing HPV infection. In the trials, women were randomly chosen to receive three doses of Cervarix or a control vaccine. Although a number of the women received fewer than the three doses, follow-up tests were completed to evaluate the effectiveness of the vaccine in all the women for a period of four years.
The analysis determined the protection from one dose is similar to that achieved by three doses of the vaccine.
"These exciting findings address the fact that nearly two-thirds of people who get HPV vaccines do not get all three doses in a timely manner," said Harper, who was a principal investigator in one of the trials included in the analysis. "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."
"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, the other HPV vaccine," said Harper.
Worldwide, cervical cancer is the third most common cancer in women. HPV types 16 and 18 are responsible for about 70 percent of cervical cancers worldwide. These and other types of HPV cause a cancer precursor known as CIN 3.
"From all studies done, we see that Cervarix protects against CIN 3 caused by all HPV types at 93 percent efficacy," Harper said.
The study is published in The Lancet Oncology with the title, "Efficacy of Fewer than Three Doses of a HPV-16/18 AS04 adjuvanted Vaccine: a Meta Analysis of Data from the Costa Rica Vaccine Trial and the PATRICIA Trial."
University of Louisville School of Medicine