A study published on bmj.com reveals that women with pre-cancerous cervical conditions can still benefit from a significantly reduced risk of reoccurring disease after receiving the HPV vaccine.
The researchers examined data of 1,350 women aged 15-26 years between 2001 and 2003 from 24 developing and developed countries. During one of two trials, the women were randomly assigned to receive either human papillomavirus (HPV) quadrivalent vaccine or placebo. The participants were then diagnosed with HPV-related vaginal or vulval diseases (including genital warts) or underwent cervical surgery. Participants received follow-up for about 4 years.
In the two trials, over 17,000 women participated, however in this study the researchers only examined women who developed HPV-related disease.
According to results from earlier studies, HPV vaccination does not reduce progression to cervical pre-cancers in women with ongoing infections at the time they received vaccination.
The researchers decided to establish whether the HPV vaccine reduces the risk of developing subsequent disease after the first definitive treatment for such pre-cancers.
They found that the risk of developing any subsequent HPV related disease among the 587 women who had received the HPV vaccine and required cervical surgery after the trials was 6.6 cases per 100 women per year, compared with 12.2 cases per 100 women per year for the 763 women who received placebo.
Using a measured called the 95% confidence interval, the team found that women who received the HPV vaccination had a 46.2% reduced risk (22.5% to 63.2%). Furthermore, they found that HPV vaccination was linked with a considerable reduction in risk of any subsequent high grade disease of the cervix by 64.9% (20.1% to 86.3%).
For HPV vaccinated women with vaginal or vulvar disease, the reduction in risk of any HPV disease after diagnosis and treatment was 32.2% (13.8% to 51.8%).
The researchers conclude that the HPV vaccination does not lower the risk of progression to disease in HPV infected women at the time of vaccination, but that the prevalence of subsequent disease among vaccinated women who developed disease after participating in these studies was lower. According to the researchers vaccination offered considerable benefit.
The researchers state that the only way to “determine the population effectiveness of vaccination” is long-term surveillance. In addition, they highlight that several programs are currently monitoring the impact and safety of these vaccinations on subsequent diseases.
In an associated report, Dr. Jane Kine from the Harvard School of Public Health says it is vital that communication of the beneficial yet complex properties of these vaccinations are clear in order to make sure that effective and successful decisions can be made on HPV vaccinated globally.
Written by Grace Rattue