The authors of the report, who examined evidence from 26 previously published studies of more than 70,000 women, also found no serious side effects associated with the vaccines.
Most people who have sexual contact will eventually be exposed to HPV. Even though exposed, most women will naturally cure the viral infection . Persistent infection, however, could lead to abnormal cervical cells called cervical "precancerous" because these cells can slowly develop cancer if left untreated.
"Cervical cancer is the fourth most common cancer among women in the world," said lead author Dr. Marc Arbyn from the Department of Cancer Epidemiology at the Belgian Cancer Center in Brussels. More than half a million cases are diagnosed each year, and about half of these women will die from the disease, he said.
Although there are many types of HPV, only a few strains increase a woman's risk of developing cervical cancer; HPV1
For the new review, Arbyn and a team of researchers evaluated study results for two commercially available HPV vaccines: Cervarix, which targets only HPV16 and HPV18, and Gardasil, which targets these strains and two HPV types that cause genital warts , aims.
None of the studies reviewed by Arbyn and his team tracked women more than For eight years – not long enough to develop cervical cancer. In order to measure the effectiveness of each vaccine, the researchers therefore examined the precancerous.
Women between the ages of 15 and 25, who were tested negative for HPV before vaccination, had a 164 risk for precancerous disease associated with HPV16 or HPV for every 10,000 unvaccinated women, compared with only two per 10,000 vaccinated women. The vaccinations also reduced the risk of cervical precancerous disease (whether or not caused by the two HPV types) from 287 to 106 per 10,000 women.
Among the same-aged women who tested positive or negative for HPV, the vaccines reduced the risk of cervical precancer-related HPV16 or HPV 18 from 341 to 157 for every 10,000 women, according to the new report. HPV vaccine also reduced the risk of precancerosis from 559 to 391 per 10,000 in this group.
In older women – who were vaccinated between the ages of 25 and 45 – the effects of the HPV vaccine were lower, the authors estimate. Unvaccinated or vaccinated, the risk of precancerosis associated with HPV16 and HPV18 decreased from 145 to 107 per 10,000 women. This is likely due to the women who were previously exposed to HPV, the authors said, adding that the vaccine offered no protection against any cervical precancer
Claims and reports that the vaccine causes neurological problems – including seizures – Arbyn and his colleagues found local reactions, such as a swollen arm, when receiving one of these two vaccines but "no increased incidence of serious side effects". However, the evaluators added that "evidence of rare potential damage … is difficult to capture in the study types studied".
Dr. Jo Morrison, a consultant in gynecological oncology at Musgrove Park Hospital in Somerset in the United Kingdom, said the allegations that the vaccine-damaging young girls "are not evidenced by the evidence". Morrison, who was not involved in the study, added, "Taking this road carries risks by reducing vaccination rates."
Overall, Morrison believes "the review calms people that HPV vaccine is effective and should be encouraged to vaccinate their daughters as recommended by the government."
Helen Bedford, a professor at the Institute for Child Health from University College London, noted that "HPV vaccine was introduced 10 years ago for 13- to 14-year-old girls to prevent infections with HPV, which can lead to cervical cancer."
CNN's Meera Senthilingam contributed to this report.