What is HPV?

HPV refers to a group of viruses belonging to the Papillomaviridae viral family that can infect humans, often through intimate skin-to-skin contact such as vaginal, anal, or oral sex. In fact, HPV is the most common sexually transmitted infection in the US, with most sexually active people becoming infected at some point in their life. 

There are lots of different types of HPV, some of which are considered to be “high-risk” because they’ve been linked to certain types of cancer, including cervical, anal, vaginal, and some head and neck cancers. For example, nearly all cervical cancer is thought to be caused by long-term high-risk HPV infection.

The good news is that thanks to the action of our immune systems, 90 percent of infections will go away by themselves within two years. However, sometimes an infection can last for longer, and if it’s a high-risk type of HPV, the damage that it causes to cells and their DNA when it infects them can cause them to multiply uncontrollably. 

The immune system can get rid of these abnormal cells too – but that’s not always the case. For cervical cells infected with high-risk HPV, they can become precancerous after around five to 10 years. After roughly 15-20 years, if those precancerous cells are left untreated, they can develop into cervical cancer, which killed around 350,000 people worldwide in 2022.

How HPV vaccines work

HPV vaccines aim to prevent the development of HPV-related cancers by stopping the viral infection from taking hold in the first place. Like other vaccines, they do this by making the immune system think it’s been exposed to the actual virus, triggering it to produce antibodies against HPV. 

The immune system then “remembers” this and so, if actual HPV viruses enter the body, it then rapidly and effectively mounts a response to prevent a full-blown infection. 

In the case of HPV vaccines, this is achieved via purified non-infectious, virus-like particles of the L1 capsid protein – capsids form the shell that encloses a virus’ genetic material. As it doesn’t contain the full virus itself, the vaccine cannot infect patients with HPV. Cervarix, for example, contains L1 protein for HPV types 16 and 18, which are the cause of most HPV-related cancers.

Depending on factors like age and the particular vaccine being given, effective immunization can generally be achieved with two or three doses, though some vaccines are now considered to be effective in just a single dose. 

What difference have HPV vaccines made?

The impact of HPV vaccines nearly 20 years after they were first FDA-approved is one that, on the face of it, looks overwhelmingly positive. 

In 2024, Public Health Scotland announced that no cervical cancer cases had been detected in women who’d been fully vaccinated since its vaccination program started in 2008. A study published earlier this year found that England is on track to eliminate cervical cancer by 2040, with incidence of the disease in those born since 1991 having dropped drastically following the introduction of the vaccine – though “eliminate” in this case means reducing the rate of incidence to 4 in 100,000.

It could soon become a similar story in the US too, with a recent study finding that just 13 women under the age of 25 died from cervical cancer between 2019 and 2021, compared to 55 between 1992 and 1994. Though other reasons for the reduction are also at play, the introduction of HPV vaccines is thought to be one of the major driving factors.

Globally, however, there’s some cause for concern. While several countries have pledged to help eliminate cervical cancer by introducing the HPV vaccine, the worldwide proportion of girls aged 9 to 14 having received their first dose stands at 27 percent, as of 2023. The World Health Organization’s (WHO) target is to reach 90 percent coverage in the next five years – which doesn’t look like a particularly realistic achievement in light of the most recent data.

Add a little more context though, and it’s not all doom and gloom. Global coverage back in 2022 was only 20 percent, meaning it increased by 7 percent in just two years. “If this rate of progress is maintained,” the WHO said in a statement, “the world would be on track to meet the 2030 target to make HPV vaccines available to all girls everywhere.” 

Nonetheless, the burden of cervical cancer is much greater in some countries than it is in others, so it’s important that efforts to reach that goal also take this into account.

The future of HPV vaccines

While the use of vaccines to prevent disease is a well-trodden path, researchers have now suggested that the HPV vaccine could also be used to treat precancerous cells before they become malignant. This could help those with abnormal cells avoid the standard treatment of loop excision, which can have side effects such as infection and scarring.

In a recent clinical trial, scientists aimed to find out if their therapeutic HPV vaccine – called Vvax001 and designed to target HPV16 – could cause the regression of a type of precancerous condition called cervical intraepithelial neoplasia grade 3 (CIN3). While this is a group of abnormal precancerous cells, rather than cancer, around one-third of CIN3 cases progress to cervical cancer within 10 years if left untreated.

Of the 18 CIN3 patients who received the vaccine as part of the trial, nine saw regression of their lesions – in three of those patients, the regression was complete. 

“To the best of our knowledge, this response rate makes Vvax001 one of the most effective therapeutic vaccines for HPV16-associated CIN3 lesions reported to date,” said principal investigator Refika Yigit, MD, in a statement. “If confirmed in a larger trial, our results could mean that at least half of the patients with CIN3 might be able to omit surgery and avoid all its possible side effects and complications.”

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.