Cervical cancer is the fourth commonest cause of cancer among women, and tragically is often diagnosed too late. It is caused by the human papillomavirus (HPV) which is easily spread by sexual intercourse. Besides cervical cancer, it can also cause genital warts and cancer of the anus and penis. Therefore, doctors recommend pre-teens of both sexes be vaccinated. Currently, Cervarix, which with another vaccine, Gardasil, is being rolled out to shield young people from HPV. A new study has found that a single vaccine shot, rather than the recommended triple dose, may be enough to protect women against cervical cancer.
Cervarix is a so-called bivalent vaccine, targeting two types of virus, HPV 16 and 18, that together are to blame for about 70% of cases. This vaccine was initially approved to be given in three doses over six months, although some countries have cautiously switched it to a two-dose schedule.
Cervarix was tested among 7,500 women in Costa Rica aged 18-25 years and more than 18,500 women aged 15-25 years in the Asia-Pacific, Europe and the Americas. Women in these trials were randomly assigned to receive either Cervarix in three doses, or a hepatitis A vaccine. However, 543 of the women in the Cervarix group received only one dose, mainly because their vaccination was discontinued due to pregnancy.
Four years after the trial, the researchers checked the health of the volunteers; and found no difference in cancer rates among those who had received Cervarix, regardless of the number of doses they had received. Researchers have called for a new randomized study to see if these findings hold true on a larger scale and beyond just four years. The authors said, "If further work validates the findings, there could be major gains for campaigns to vaccinate young women in poor countries."
Co-author Aimee Kreimer of the US National Cancer Institute said, "If one dose is sufficient, it could reduce vaccination and administration costs as well as improve uptake. This is especially important in less developed regions of the world, where more than 80% of cervical cancer cases occur."
The new research is published in the The Lancet Oncology