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What we can learn from the HPV vaccine

It is sometimes hard to remember that cervical cancer used to be one of the most common and deadly cancers in women.

This article was originally published in the Montreal Gazette

While we talk a lot about the COVID vaccine, another vaccine made news last week. A new analysis from the U.K. has estimated that the widespread use of HPV vaccine has reduced cervical cancer rates by roughly 90 per cent and according to the authors has “almost eliminated cervical cancer” for women born after 1995.

It is sometimes hard to remember that cervical cancer used to be one of the most common and deadly cancers in women. But since the 1950s, mortality from cervical cancer has been plummeting . It fell by two-thirds between 1950 and 1997 largely due to the introduction of the PAP smear by Georgios Papanikolaou in 1941. The PAP smear was a significant invention, not just because of the impact it had on cervical cancer but also because it proved the premise that you could identify cancer by spotting abnormal cells under the microscope. This discovery, which seems obvious to us today, was groundbreaking in the 1940s and demonstrated that you could spot suspicious cells early before they transformed fully into cancer.

The PAP smear is useful because it allows clinicians to identify cervical intraepithelial neoplasia (CIN), essentially a pre-cancerous lesion of the cervix. CIN usually precedes a cancer diagnosis by several years and its identification and early treatment can prevent cancer from developing.

The benefits of the PAP smear are evident from the epidemiological data. But the technique has its drawbacks. It is resource intensive and requires regular screening and follow-up and it needs patients to come into regular and repeated contact with the health care system for testing. It works extremely well here in developed countries where the benefits of falling cervical cancer mortality have been well documented. But cervical cancer remains an issue in the developing world, where the death rate is high and regular screening with PAP tests is hard to implement. The advantage of the HPV vaccine — and this is true of most vaccines — is that they are inexpensive and cost effective. They can be rolled out fairly easily over a wide area and are much less resource-intensive than a strategy that requires regular testing and follow-up.

Also, the PAP test allows you to catch and treat the pre-cancerous lesions early but it doesn’t prevent them from happening in the first place, whereas the HPV vaccine actually prevents the cancerous changes from developing. Since most cervical cancer is due to infection with HPV, a vaccine against the virus effectively prevents the cancer. A 2018 Cochrane review , which included data from 26 trials and more than 70,000 patients, demonstrated that in females 15-26, the HPV vaccine decreased rates of CIN by 99 per cent. A 2020 study from Sweden showed a similarly massive 88 per cent drop in cervical cancer rates in women vaccinated before age 17.

The current U.K. analysis essentially confirms these earlier findings and estimates that the vaccine rollout in England prevented more than 17,000 cases of CIN. The benefit was larger in younger age groups because, as HPV is a sexually transmitted infection, the greatest benefit is seen when you vaccinate younger patients who have not yet been exposed to the virus. The authors point out that the high vaccination rates in U.K. girls aged 12 and 13 almost eliminated cervical cancer and CIN in that group over the 10 years of follow-up.

Unfortunately there is often resistance to vaccines and the situation is not helped by news stories that overhype the risks. The now infamous Toronto Star headline about the HPV vaccine’s dangers had to be retracted after the newspaper ultimately admitted that they had not acknowledged the wealth of scientific data showing no increased risk from vaccination. I will no doubt spend the rest of my life advocating for the broad use of scientifically proven vaccines, because when more people get vaccinated, less people get sick. It’s as simple as that.


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