HPV: 10 years of the vaccine
Human Papilloma Virus, or HPV, is the name for a group of viruses that commonly cause verrucas, warts, genital warts and cervical cancer. And they are very common. The infection usually resolves itself, but in some cases it leads to damage to the DNA in the infected cells, which can result in cancer. This is why we have a screening programme to look for these changes and try to pick up the disease early before it can spread. Just over ten years ago, a vaccine against the highest risk forms of the virus was introduced; in Australia boys and girls received it, but in other places it was given just to girls. The UK was one of them. But 2019 will see it also being offered now to boys, as well as changes to the way we screen for HPV infection. Margaret Stanley helped to develop the HPV vaccine at Cambridge University, and she spoke with Chris Smith. First up, Chris asked Margaret what 10 years of data shows about the vaccine; does it work?
Margaret - Well I can give you the information from the UK and the UK has had a spectacularly successful vaccination programme, and we're seeing the results of that now and I can quote what's happened in Scotland. The girls who were vaccinated in 2008 in Scotland aged 13/14, by the time they were 20, in 2015/16, came up for their first cervical cancer smear - because in Scotland, at that time, you were getting smears at 20 - so we know what proportion of those girls we expected to have the pre-cancer - that's what the cancer screening programme's about - and what proportion did.
In fact there was a reduction of eighty six per cent in the pre-cancers in that group of vaccinated girls. That's spectacular. Part of the reason why is in that young group of girls those two very high risk viruses that the vaccine targets are the ones that cause most of the pre-cancers and the cancers. So the vaccine is stunningly successful. Same data from Australia; same data from Denmark. Wherever you've got a high vaccine coverage - now I want to emphasise that: we've been really successful in the UK because almost 90 per cent of our 13 year olds are vaccinated, whereas in other countries where it's much lower you're not getting the result.
Chris - Yes so the data you quoted is for people who have been vaccinated against people who would have been otherwise identical to that group and haven't. So if we look at those people who haven't, roughly what number of cervical cancers are we seeing or pre-cancers are we seeing in those people normally?
Margaret - The pre cancers sort of peak in the 20s, and you expect to see about two per hundred individuals for the pre-cancers. Now not all those pre-cancers go on to cancer, but those two individuals will have to be treated. So what we're doing is taking out almost all of those pre-cancers, losing that treatment. If you haven't been vaccinated, however, you've got to be screened, and you still ought to be screened even though you're vaccinated, because not all of the HPVs that cause cancer are targeted by the vaccines, but your risk is massively reduced.
Chris - What was the rationale, was it just cost, for only going for the girls and not vaccinating the boys in countries like the UK?
Margaret - Well it's because genital HPV is a sexually transmitted infection, and if you immunise one gender then you protect the other gender. And so decisions about who to vaccinate, when and how many, is based on modelling and on health economic policy. So the models said well if you can get up to 85-90 per cent of girls vaccinated, we won't need to vaccinate the boys. But it turns out that men get cancer of the throat, which is caused by HPV and they're four times more likely to get it than girls.
Chris - And the vaccine will stop that?
Margaret - Well I have to be very careful; I have no data from trials that says that the vaccine will stop the cancer. I can tell you that the vaccinated people lose their infection in the mouth, so it prevents the infection in the mouth. And you know I'm a simple soul, if you don't have the infection you won't get the cancer.
Chris - Now you mentioned that the vaccine represents some of the highest risk forms of the virus, but it doesn't cover all of them. So we're still having to do cervical screening. Why can't we add the missing viruses into the vaccine and if it's so successful?
Margaret - Well there’s a second generation vaccine, which is commercially available, and that's the one actually which is now being delivered in Australia and the USA, but the decision hasn't been made yet in the UK as to whether to put that into our programme.
Chris - And that does represent these other forms that are missing at the moment?
Margaret - Well it represents, for the sort of global take on this is the vaccine that targets the two high risk viruses, which is what we currently use, will get rid of 70 per cent of cervical cancers worldwide. You put this other one in which has another four high risk HPVs, you'll get rid of up to 90 per cent of cervix cancers worldwide; but you'll still have a little rump of cancers which are not covered by the vaccine.
Chris - So we still need to screen and that brings me on to my only point which is can we use the learning that's gone with the study of human papillomaviruses together with much better diagnostic techniques that we now have where we can screen for DNA and things like that now, rather than just having to look at cells under microscopes. Can we use this knowledge to do a better or better screening job?
Margaret - Yes the screening programme in England and the rest of the UK is going to change in 2019. From the first analysis being looking down the microscope itself to in fact detecting DNAs of these high risk viruses. You'll still come for your smear at 25, but instead of that smear being looked at down the microscope first, it will be tested for DNA. If it's DNA positive for the virus, then the screener will have a look at those cells, and if the cells are normal then you'll go back into the programme and be asked to come back and have another screen in about a year's time to make sure you've got rid of the virus.
Chris - Crucially if it's negative you need go no further at that time. So it’s going to save loads of money and time.
Margaret - It's not only that, it's going to save all the hassle of going for a smear, and it's a much easier and much more convenient. More importantly it's more sensitive. The trouble with cervical screening is it's a wonderful public health intervention but although it's very specific, it's not very sensitive.