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In a study that examined the vaccine's effectiveness in a large population of Australian women, the University of Queensland researchers claim their finding suggests HPV vaccination is effective when given to a broad swath of individuals.
HPV can lead to precancerous lesions of the cervix, genital warts and cervical cancer, said Dr. Subhakar Mutyala, associate director of Scott & White Cancer Institute at Texas A&M College of Medicine. Mutyala, who was not involved in the study, said clinical trials have shown that HPV vaccination in young women helps prevent cervical cancer.
Australia was the first country to create a national vaccine program using public funds, and health officials there began vaccinating women against the virus in 2007.
The study authors collected data from 2007 to 2011, using a population register in Queensland. More than 100,000 women, who ranged in age from 12 to 26, received their first-ever Pap test during that period. Pap tests look for precancerous and cancerous lesions on the cervix.
To learn more about the effectiveness of the vaccine, the researchers divided the women into three groups based on results from their Pap tests: One group tested positive for precancerous and cancerous lesions; one group tested positive for abnormal but not precancerous lesions; and a third "control" group had normal Pap test results.
The authors then examined the effectiveness of the vaccine in "sexually naive" women who had no prior infection, some of whom had received one dose, two doses or three doses of the three-dose HPV vaccine.
The authors reported that three doses provided 46 percent protection against "high-grade" cervical abnormalities, such as precancerous lesions, and 34 percent protection against other cervical abnormalities, such as genital warts, compared to women who had not received the shots.
The researchers also found that two doses of the vaccine provided 21 percent protection against high-grade abnormalities and other cervical abnormalities. One dose of the vaccine did not shield from infection.
The findings are published online March 4 in bmj.com.
"It's an important study," said Dr. Jeffrey Klausner, a professor of medicine (infectious diseases) and of public health at Ronald Reagan UCLA Medical Center. "They compared women with cervical disease and women without, and they found a significant protection rate, nearly a 50 percent reduction in risk in women vaccinated versus unvaccinated women."
Mutyala noted the study shows that in real life -- not just in a controlled research setting -- the vaccine has a significant impact on the health of women.
"The goal is to eradicate the HPV virus in our entire population, and the study actually shows the vaccine is working in Australia," Mutyala said. "It's decreasing those cellular level, microscopic-level abnormalities picked up on a Pap test."
In a separate study published last month in the Journal of the National Cancer Institute, Danish researchers reported that young women who received HPV vaccination had a much lower risk for precancerous lesions compared to those who weren't vaccinated.
According to the U.S. Centers for Disease Control and Prevention, about 15,000 cancers caused by HPV occur in women each year, and cervical cancer is the most common type. Approximately 7,000 cancers caused by HPV occur in men, with throat cancers the most common.
Two HPV vaccines are licensed by the U.S. Food and Drug Administration and recommended by CDC -- Cervarix and Gardasil. Mutyala said the vaccines are approved by the FDA for use in boys and girls aged 9 and up. He said only about one-third of girls in the United States are currently vaccinated, and only about 7 percent of boys.
Klausner said the United States should have better HPV public education and vaccination programs.
"It's shameful that in the United States, the richest country in the world, we can't vaccinate against cancer," said Klausner, who recently reviewed HPV vaccination in Rwanda, Africa, where the vaccination rate is 97 percent. "The vaccine works and it's safe."
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