A Vaccine For Cervical Cancer
Margaret - It has always been realised that cervical cancer is a sexually transmitted disease because celibate people don't get it! However, it was only in the 1970s that people discovered that cervical cancer is caused by a virus from a common family called papilloma (the same virus that causes warts). At this time, there were two ways to make virus vaccines: one was to deactivate the virus; the other was to grow it up in the laboratory over a period of time to change it so it was no longer dangerous, or pathogenic; you could then inject it into people to give them immunity. But neither of these methods worked with papilloma. In the 1980s, two scientists in Australia came up with an answer. They found a way to construct the protein 'shell' of the virus in the laboratory without having to grow it in tissue culture. Injecting this protein 'shell' into the body should cause the body to mount a defence against the shell (thinking it was real papilloma virus), making that person immune. This made the possibility of vaccine development highly probable, but no-one was sure it would work. Extensive trials over the last five years have shown that it does.
Chris - Does having sex more often mean a woman is more likely to get it?
Margaret - Yes and no. What really matters here is knowing what your partner has been doing! When people have sex, they exchange a whole zoo of microbes. Most of these are perfectly harmless, but some are ones you want to stay clear of. If you have sex with lots of people, you acquire a very exotic zoo that is more likely to contain some disease-causing microbes. Therefore, someone who has had sex with very few people can contract the virus just because their partner has had many partners beforehand. Individuals particularly at risk are those who have lots of sex and/or unprotected sex, so you have to be sensible about it.
Chris - What about age as a factor?
Margaret - If you have sex at an early age, the cervix is very sensitive to the virus and is more likely to be affected. By around 20 years old, the cervix has started to settle down, and the risk of contracting the virus is lower. However, anyone who has sex is at risk, so in that sense, there is no age when you are completely safe.
Chris - Cervical cancer is the leading cause of cancer death in women worldwide, and kills 3500 women in Britain each year. Do you think this may soon be a thing of the past?
Margaret - You must never say that we can get rid of something completely, but we can certainly reduce it substantially. The vaccine that is likely to be first used, if given in the most optimal way, is likely to get rid of 70-80% of cervical cancers without any other intervention. However, it must be given before girls have sex, which in 2004 is realistically to 10 year olds !
Chris - How long will the protection last?
Margaret - That is a critical point, but the answer is that we don't know. We have only been having controlled trials for the past four years, which isn't really long enough to know how long protection will last. However, the results coming through are showing that there is protection up to four years, which is a long time for this type of vaccine. We need further tests to see if the vaccine will also work in men.