HPV Vaccines to prevent cervical cancer: Why are they so important?

Did you know that the Human Papillomavirus (HPV) is the most common sexually transmitted infection? 8 out of every 10 sexually active individuals will get HPV in their lifetime. Luckly, not all cases lead to cancer but almost 90% of cervical cancers are in fact related to HPV. Here is what you need to know.

Cervical Cancer

Over 500,000 people around the world develop cervical cancer every year, and the main cause of this disease is persistent infection with certain types of HPV.


The diagnostic process may include tests such as cervical cytology, also known as a Pap smear, which consists of gently scraping cells from the cervix with a small brush or spatula, to later examine these cells under a microscope.

Other procedures to diagnose cervical cancer include:

  • HPV testing 
  • Colposcopy, which is a visual examination of the cervix
  • Biopsy of the cervix, consisting of collecting a small tissue sample for analysis


Depending on the stage of the cancer, the treatment may include surgery, to remove the cancerous tissue, radiation therapy, chemotherapy, or a combination of the last two. In cases where complete remission is not possible, the objective of treatment is to improve the patient’s quality of life and increase their lifespan. 

Human Papillomavirus (HPV) and cervical cancer  

There are over 180 subtypes of HPV, all of which share one key characteristic: they infect the cells of the surface of the body (skin or mucosa). They are usually classified as being non-genital or genital HPV.

Human Papillomavirus is transmitted mainly through skin-to-skin contact with someone who is infected, specifically with the lesions caused by the virus. Many different areas of the body can be affected, and whether infection occurs will depend on the virus subtype, and the area that has been exposed to it. It should be noted that the subtypes that have been linked to cervical cancer are transmitted through sexual intercourse. 

Genital HPV is linked to cancer

Genital HPV infections are so common that just in the US around 18 million people become infected every year, but as we mentioned before, this does not mean that all these people will develop cervical cancer. 

Most genital HPV infections have no symptoms and will resolve on their own within two years. Only some subtypes of HPV can lead to genital warts or certain types of cancer, and while HPV is mostly linked to cervical cancer, it can also cause cancer in other areas such as the penis, anus, vagina, vulva, mouth, and throat. 

The most important HPV subtypes to be aware of are:

  • Type 6 and 11, which are the main cause of genital warts. Because they don’t lead to cancer or other serious health problems, they are considered “low-risk HPV”.
  • Type 16 and 18 cause around 90% of anal cancers and 70% of cervical cancers. These are called “high-risk HPV”.

Although HPV related cancers are mostly caused by subtypes 16 and 18, there are at least a dozen subtypes that can lead to cancer, including types 31, 33, 45, 52, and 58. 

How does it evolve from an infection to cancer? HPV causes changes in the infected cells, and over time, if there are other risk factors, these develop into pre-cancer lesions, that can progress to cancer. 

HPV vaccine and cancer prevention

The main strategy to avoid potential diseases caused by HPV is to prevent the infection from happening in the first place through vaccination, which protects against some of the most important subtypes. The objective is to make people immune to these subtypes, meaning that even if they come into contact with them, they will not become infected. 

Types of HPV vaccines

There are currently 3 different types of HPV vaccines available, and the main difference between them is the HPV subtypes they each protect against:

  • Human papillomavirus 9-valent vaccine: Protects against HPV types 6 and 11; types 16 and 18; and types 31, 33, 45, 52 and 58. This vaccine is the only one currently available in US.
  • Human papillomavirus quadrivalent vaccine (HPV4): Protects against types 6, 11; and types 16 and 18. 
  • Human papillomavirus bivalent vaccine (HPV2): Protects against types 16 and 18. 

All the vaccine types are administered in two or three doses depending on the age of the person at the time they received the first shot.

Safety of HPV Vaccines: Side Effects and other Considerations

As with most medicines or treatments, there may be situations in which a vaccine may be contraindicated for safety concerns: due to a person’s specific circumstances. In the case of HPV vaccines, they should not be given in the following situations:

  • In the case of a severe allergic reaction after a previous dose or to a component of the vaccine. 
  • Pregnancy. If a woman becomes pregnant after receiving the first or second vaccination dose, she will be given the remaining doses after pregnancy.
  • Sickness (with or without a fever). In this case, the vaccination can be postponed and given once the illness resolves. 

Since HPV vaccines became first available in 2006, over 500 million doses have been given to people all over the world. The safety of the HPV vaccine has been regularly reviewed by the Global Advisory Committee for Vaccine Safety, using all the information available globally. Except for rare cases of anaphylactic reactions, no serious safety issues have been reported. 

The most common side-effects of the human papillomavirus vaccine are mild and local reactions of pain, tenderness, or swelling at the injection site. In some cases, although less frequently, it can sometimes be linked to the onset of headache, dizziness, myalgia, arthralgia, and gastrointestinal symptoms including nausea, vomiting and abdominal pain. 

World Health Organization HPV Vaccine Recommendation

One of the goals adopted by the World Health Assembly, a decision-making body of the World Health Organization (WHO), is to eliminate cervical cancer as a public health problem by 2030, leaving the ratio at less than 4 cases per 100.000 women, mainly through HPV vaccination.

  1. They have also set out to achieve different targets:  
  • World-wide HPV vaccination of 90% of girls by 15 years of age.
  • Screening of 70% of women with high performance tests by the age of 35 and again by the age of 45.  
  • Treatment 90% of women diagnosed with cervical disease spanning from pre-cancerous lesions to invasive cancer cases.

Currently, only 32% of the world’s ten-year-old girls have been vaccinated against HPV, meaning that 68% still need to be vaccinated. Interestingly, this large proportion of unvaccinated girls are all located in the same 65 countries. Therefore, making it easier for these countries to carry out vaccination campaigns is fundamental to reach the World Health Assembly’s goals.

Latest guidelines and research

In 2022, the WHO published an update on HPV vaccines, addressing key issues, including the dosing regimen. 

Originally, when the first vaccines became available, three doses were recommended. Over time, this was brought down to two doses in children over the age of 9. Later studies have shown that a single dose is effective in preventing cervical cancer in around 97.5% of people, meaning that the first shot is crucial. Currently, although 2 or 3 doses are considered ideal, the official recommendation states that at least one dose should be administered to children between 9 and 20 years of age.

This change in the guidelines is especially relevant in countries where implementing vaccination campaigns is difficult and too expensive. It implies that with the same number of vaccines, twice as many people can get vaccinated and still have a high degree of protection. This shift in dosage will represent a game-changer for many countries in their efforts to offer HPV vaccinations access to their citizens.