Vaccines designed to prevent infection with human papillomavirus (HPV) are effective in protecting against pre-cancerous cervical lesions in women, particularly in those vaccinated between age 15 and 26, according to a large international evidence review.
The research by scientists at the scientific network the Cochrane Review also found no increase in the risk of serious side effects, with rates of around 7 percent reported by both HPV-vaccinated and control groups.
"This review should reassure people that HPV vaccination is effective," Jo Morrison, a consultant in gynecological oncology at Britain's Musgrove Park Hospital, told reporters at a briefing about the review's findings.
She noted that some campaign groups have expressed concern about HPV vaccines, but said this review had found no evidence to support claims of increased risk of harm.
HPV is one of the common sexually transmitted diseases. Most infections do not cause symptoms and go away on their own, but when the immune system does not clear the virus, persistent HPV infection can cause abnormal cervical cells.
These pre-cancerous lesions can progress to cervical cancer if left untreated. HPV is a leading cause of cancer deaths among women worldwide, according to the World Health Organization.
Drugmakers GlaxoSmithKline and Merck make vaccines that protect against HPV.
The Cochrane research pooled data and results from 26 studies involving more than 73,000 women across all continents over the last eight years.
The researchers found that in young women who tested negative for HPV, vaccination reduced the risk of developing precancer. About 164 out of every 10,000 women who got placebo developed cervical pre-cancerous lesions, compared with two out of every 10,000 who were vaccinated.
Looking more broadly across all women in the studies, regardless of whether they had previously had HPV or not, the vaccines were found to be slightly less effective, but still reduced the risk of cervical precancer from 559 per 10,000 to 391 per 10,000.
Experts not directly involved in the review said its findings were robust and important.
"This intensive and rigorous Cochrane analysis ... provides reassuring and solid evidence of the safety of these vaccines in young women," said Margaret Stanley, a specialist in the pathology department at Cambridge University. "It reinforces the evidence that preventing infection by vaccination in young women ... reduces cervical precancers dramatically."