1 Dose of HPV Vaccine May Protect As Well As 3, Study Says
A single dose of a human papillomavirus, or HPV, vaccine may be as effective in preventing certain HPV infections as three doses—the currently recommended course of vaccination, a recent study said.
The study, recently published in The Lancet Oncology, found that Cervarix is 93 percent effective at preventing pre-cancerous lesions known an CIN 3.
Dr. Diane Harper, Rowntree endowed chair and professor in the Department of Family and Geriatric Medicine at the University of Louisville School of Medicine, is co-author and one of the principal investigators of the study.
Another drug, Gardasil, became available in 2006. The Centers for Disease Control and Prevention report that most of the more than 46 million doses of HPV vaccine that have been administered were of Gardasil.
While both vaccines have antigens to the types of HPV that mostly cause cancer, Cervarix has a more powerful adjuvant—which gives it a long-lasting immune response, Harper said. Gardasil prevented CIN 3 lesions 47 percent of the time.
In 2009, the FDA approved Cervarix to prevent cervical cancer and precancerous lesions caused by HPV types 16 and 18.
Gardasil may be the most widely used, it may not be the best option for girls and women, Harper said. She said not only is Cervarix superior to Gardasil, it can also offer the same level of effectiveness with just one dose.
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.
"If you get three doses of Cervarix, you will gain this 93 percent efficacy against true cancer precursors regardless of the HPV type and that will last for nine and a half years," Harper said.
Two-thirds of women who start the three dose program never finish it, which results in wasted doses and missed protection, said Harper.
In 2013, Kentucky’s HPV vaccine completion rate for females age 13-17 (26.8 percent) was lower than the national rate (37.6 percent). Data on males completing the series are incomplete for Kentucky. The initiation rate for Kentucky males ages 13-17 (19 percent) was lower than U.S. males (35 percent), according to the University of Kentucky Markey Cancer Center.
The Vaccines for Children Program provides free HPV vaccines for children who qualify, but out of the nearly 700 providers who participate none provide Cervarix.
"If they would be willing to get one shot and then be willing to get screenings, we can really make a dent in the number of abnormalities that happen in women's cervices on Kentucky. It can really make a difference," she said.
Harper said she isn't pushing for women not to get three doses of Cervarix, but she wants them to worry unnecessarily if they don't complete the series of shots.
"Three doses is still best, but if you can't finish three doses even just getting one dose in is better than nothing," she said.