The News of the World claimed today that the Government has opted for the weaker of two possible cervical cancer vaccines because it is cheaper. The paper calls it a “scandal” but the story has been rather mangled resulting in some misleading information. Here, we try and set the facts straight.

First, a quick recap. The vaccines are designed to protect young girls from infection by HPV – the virus that causes cervical cancer. There are two vaccines – Gardasil and Cervarix – and the Department of Health picked Cervarix for use in a nationwide vaccination programme.

But according to the News of the World, it’s a bad choice.

“A Department of Health memo seen by the News of the World shows that, while Gardasil is 100 per cent effective, Cervarix has only a 70 per cent success rate against the most common varieties of the disease…

“The [Department of Health] website also claims “the vaccine is 99 per cent effective”. It does not mention that this figure applies to only two of the 100 HPV strains.”

There are many types of HPV. Both vaccines, Cervarix and Gardasil, protect against the two types that are most commonly associated with cervical cancer – HPV16 and HPV18. Between them, these two types cause 70 per cent of cervical cancers.

Against these two types of HPV – the ones it was designed to target – Cervarix provides very effective prevention. At the very least, it is 90 per cent effective, and in some clinical trials, it provided complete protection. Gardasil is similarly effective.

So the News of the World isn’t comparing like for like here. Against “the most common varieties of the disease”, both vaccines provide extremely high levels of protection. And overall, both vaccines could only prevent 70 per cent of cervical cancers, because they are only designed to treat two cancer-causing strains of HPV.

“[Cervarix] is only 30 PER CENT effective against some new strains.”

As we’ve said, Cervarix is only designed to vaccinate people against two types of HPV. Gardasil tackles two further strains that can lead to genital warts, but neither of these causes cervical cancer.

The good news is that both vaccines can also provide some protection against rarer cancer-causing types of HPV. In one clinical trial, Cervarix was 94 per cent effective against HPV45 and it was 55 per cent effective against HPV31. If you rank HPV strains in terms of the numbers of cervical cancers they cause, these two types would rank third and fourth.

So Cervarix isn’t completely effective against these strains, but then again, it wasn’t designed to be. The fact that it does should be seen as a happy bonus rather than a cause for derision. Criticising it on such grounds would be like chastising it for not protecting against the common cold!

All in all, the vaccine is an exciting development, not a cause for ill-considered conspiracy theories. The only real message to take away from this story is one that we have said before – Cervarix will help to prevent many cases of cervical cancer, but not all.

For the moment, it is absolutely essential that everyone, even those who have been vaccinated, attends cervical cancer screening when invited. The screening programme is still our best way of preventing cervical cancer and will remain invaluable for decades to come.

We’ve blogged about the vaccine before, and you can also read an in-depth analysis of it on our website.