Yesterday, The Guardian Science Blog has helped me launch the debate on HPV vaccination. There you can read a blog post on my first findinds and thoughts.
In the past weeks I’ve come across very interesting studies about the two vaccines that can prevent cervical cancer.
First of all, in this Cancer Research UK’s page you can read very clear information about the human papillomavirus.
Secondly, it is worth reminding the main differences between the two vaccines.
1 – Cervarix:
2 – Gardasil:
Just a few days ago, the Department of Health has responded to my Freedom of Information (FOI) request. My main questions were related to the scientific evidence that led the UK Government to choose Cervarix over Gardasil. They clearly admitted that the Joint Committee on Vaccination and Immunisation (JCVI) recommended the use of Gardasil as it protects against not only cervical cancer but also genital warts, so the decision was ultimately determined by matters of cost-effectiveness. We all would like to know how much the UK has paid for the vaccine, neverhteless the FOI response stated that:
The information in question has been identified at all stages as being commercially sensitive and we have considered your request very carefully, taking account of all the circumstances. In short, as explained below, we have reached the conclusion that the information you have requested should be withheld as exempt under FOIA section 43(2) which is available to protect commercial interests.
Now with the help of Dr Peter English, who is editor of Vaccines in Practice magazine and has been a consultant on vaccine boards for various vaccine manufacturers, I found out that the scientific evidence is not yet enough to permit any manufacturer to make claims of duration of efficacy beyond that which has been proved. One should not forget that such HPV vaccination programmes have been implemented a few years ago only, so we need to wait and remain monitoring the effectiveness of the programmes in order to draw conclusions.
One other thing I found out is that scientific evidence released after the UK Government went for Cervarix is that this GSK vaccine may offer cross-protection to other cancer-causing HPV strains that Gardasil doesn’t. Check out this study:
– Human Papillomavirus (HPV) Vaccines: Limited Cross-Protection against Additional HPV Types, published in The Journal of Infectious Diseases
As you can see from this table, Cervarix offers cross-protection to HPV 45, which according to this study should be given priority in cancer prevention.
In addition, there are other worth mentioning aspects raised by Dr Peter English. Please note that these are his own opinions and not those of his employer.
Cervarix and immunity
Cervarix, which only contains the two oncogenic types, also contains an “adjuvant” – a chemical which makes the vaccine stimulate a higher level of immunity. GSK, who make Cervarix, claim that this means that the vaccine generates a stronger immune response, with more antibodies produced (a higher concentration of antibodies to the vacine in the blood stream – “higher serum levels”). As serum levels fall gradually over time, they suggest that this means that people given Cervarix will have immunity that will last for longer.
Gardasil, by contrast, while it protects against genital warts, is unadjuvanted. The antibody levels it generates are not as high as following Cervarix. Sanofi Pasteur Merieux, who make (or market) Gardasil in Europe claim that the levels are sufficient to give good immunity that is likely to last as long as it’s needed.
Are three doses necessary?
If antibody levels continue to fall as the graphs – and experience with other vaccines etc. – suggest, both vaccines are likely to provide protection for 10-25 years – but it’s hard to know for how much longer than Gardasil Cervarix will actually protect women. A single booster dose years after the original course could be expected to push antibody levels back up to the levels they were at after initial course of vaccine; and with the quantity of vaccine that is being produced for world-wide use, it’s likely that the cost will be considerably lower in 15 years time.
Have you found this interesting? Have you got any information that may be relevant to the investigation? I am particularly interested in knowing which countries use which vaccine in their (perhaps non existing) vaccination programmes. We know that both vaccines have been approved in most countries, but which one do their governments pay for – and which one does private care tend to go for?
I’ve received many emails and tweets so far. They all have been very useful in my research. Please contribute as well by commenting this blog post!