By Alice Forster, on 26 May 2016
What is HPV and how is it linked to cancer?
Around 5% of all cancers worldwide are caused by the human papillomavirus (“papi-lo-ma-virus”) or HPV. More and more people are aware that HPV causes cancer of the cervix (the neck of the womb) in women, but HPV can also cause cancers of the penis, anus, vagina, vulva and mouth and throat. The virus is spread by skin to skin contact, including sexual contact. There are many different types of HPV. Some types cause cancer, while others cause warts that people get on their hands, feet or genitals and these types do not cause cancer. The types of HPV that cause cancer are so common that HPV is the most frequent sexually transmitted infection in the UK. In most people the cancer causing types of HPV cause no problems and the virus goes away on its own. However, some people do not get rid of the infection. If the infection stays for many years it can turn into cancer.
In the late 1990s and early 2000s two vaccines were developed that protect against the two types of HPV that cause around 80% of cervical cancers. Girls who are aged 12-13 years old in Year 8 at school are now offered one of these vaccines as part of the childhood immunisation programme. The vaccine that is used as part of the UK programme also protects against two types of HPV that cause genital warts. Recently, a third HPV vaccine called the nonavalent or 9-valent vaccine has been licenced for use in the UK, as well as in the USA and elsewhere in Europe.
The new 9-valent vaccine
The 9-valent vaccine, as the name suggests, protects against 9 types of HPV – that means protection against an extra 5 HPV types compared with the other two vaccines. These 9 HPV types cause up to 90% of cervical cancers, so an additional 10 in every 100 cervical cancers could be prevented.
Where does behavioural science fit in?
The invention of these vaccines is a fantastic step forward towards wiping out cervical cancer, but this can only happen if people get the vaccine and we know that many people are not doing so for a variety of reasons. The benefits of the HPV vaccine will be greatest if most people get the vaccine, however as with all healthcare decisions, the decision to get the HPV vaccine should be an individual informed choice. In our new paper, we look at how we can use our understanding of why people don’t get vaccines, specifically the HPV vaccine, to try to increase uptake of the 9-valent vaccine.
Reason 1: Will the 9-valent vaccine overload the immune system?
Some parents worry that vaccines overload the immune system and others worry that particular ingredients make vaccines risky for their children. Parents consider combination vaccines to be risky for both of these reasons as they are seen as containing a greater number of ingredients. The 9-valent vaccine is not a combination vaccine, but it protects against 9 types of HPV compared to 2 or 4 types of HPV with older HPV vaccines and might be seen as more dangerous. However, parents should be reassured that the 9-valent vaccine is safe and has been licensed for use in the UK, USA and the rest of Europe. There is also no evidence that vaccines overload the immune system.
Reason 2: ‘I’ll wait to decide until there’s more evidence that it will protect my daughter in her twenties’
Many parents have said that rather than giving their 12 or 13 year old daughter the vaccine (as recommended) they would rather wait until their daughter became sexually active so that she may be protected when she ‘really needs it’. However, the HPV vaccine is likely to give protection against HPV for decades and works better if it is given at a younger age. Parents may also find it difficult to get the vaccine for their daughter outside of the routine immunisation programme. Parents should be reassured that 12 to 13 is the right age for their daughter to get the 9-valent vaccine.
Reason 3: ‘It’s so new, the government can’t know about the long-term side effects’
Because the vaccine is relatively new, some parents say that they are worried that the vaccine has not been monitored for long enough. However, vaccines go through many years of testing before they become available to the public. There is no evidence that the HPV vaccines are unsafe or cause side-effects other than temporary mild/moderate pain, swelling, redness and itching.
What else can be done to increase uptake of the 9-valent vaccine?
Scientists have looked at all of the published research studies that have tried to improve uptake of HPV vaccines. These show that uptake can be improved by doing things like sending reminders to parents and running school-based immunisation programmes like we have in the UK. In the USA, where the vaccine is given in a clinic setting, parents are most likely to get their daughter vaccinated if a doctor recommends that she has it. The language that the doctor uses to make that recommendation is also important.
The 9-valent HPV vaccine is a fantastic opportunity to prevent even more cancers that are caused by HPV. Parents can be reassured that the HPV vaccines are safe and will provide protection for their children against a number of cancers for many many years.