Human Papillomavirus (HPV) Vaccine
The Virus
The Human papillomavirus (HPV) is one of the most common reproductive tract infections responsible for a variety of cancers and other conditions in both men and women. Some of them have been classified by the International Agency for Research on Cancer as “high risk” (carcinogenic) in humans. HPV-16 and HPV-18 are the most common carcinogenic types, responsible for almost 70% of cervical cancers, as well as many cases of penile cancer, anal cancer, oropharyngeal carcinoma, and cancers of the head and neck. HPV types 31, 33, 45, 52, and 58 together account for 15% of cervical cancers. HPV-6 and HPV-11 are the two primary “low-risk” (non-carcinogenic) types, which cause anogenital warts. Women who are infected with one type can also be infected with others at the same time.
Disease Burden
As of 2017, the World Health Organization estimates that the worldwide prevalence of HPV among women is 11.7%. Latin America and the Caribbean have a prevalence of 16.1%, the second-highest prevalence for women after Sub-Saharan Africa (24%).
The prevalence of HPV among men is high in all regions of the world (21%) and peaks at a slightly higher age than women. The prevalence of any HPV type at the penis, in particular, is 18.7%; at the scrotum, 13.1%; and at the perineal region, 7.9%. Men who have at least three-lifetime partners have 4.5 times the odds of contracting HPV of any type when compared to men with fewer lifetime partners.
Persistent infection with a high-risk type of HPV is strongly associated with progression to cervical cancer. Globally, approximately 530,000 new cases of cervical cancer develop per year, causing about 266,000 deaths. These numbers vary by region, and lower-income regions are where the majority of cervical cancer cases occur. It is estimated that one in every 100 women in developing countries will have cervical cancer before the age of 75.
In the Region of the Americas, each year, approximately 83,000 women are newly diagnosed with cervical cancer and more than 35,000 women die from the disease. Over half of these women are under 60 years old.
Who is at risk
Anybody who is sexually active is at risk of HPV infection and women with persistent infection with a high-risk type of HPV are at risk of cervical cancer. Immunocompromised individuals, including those with HIV, are more likely to have persistent HPV infection and faster progression to cancer.
HPV is one of the most common sexually transmitted infections in the world and is usually-- though not always-- contracted and spread during sex or skin-to-skin sexual contact with somebody who has the virus. It can be spread even when condoms are used, and even in mutually monogamous relationships.
Because HPV resists desiccation (extreme dryness) and disinfection, it can survive for a long time on the surfaces of objects. As such, HPV can also be spread through objects or materials that may have come into contact with the infection. It can also be transmitted via direct contact with cuts and abrasions from an infected individual, and in rare cases, it can be spread during birth via mother-to-child transmission.
Transmission
HPV is one of the most common sexually transmitted infections in the world and is usually—though not always—contracted and spread during sex or skin-to-skin sexual contact with somebody who has the virus. It can be spread even when condoms are used, and even in mutually monogamous relationships. Most people will become infected with HPV during their lifetime.
Because HPV resists desiccation (extreme dryness) and disinfection, it can survive for a long time on the surfaces of objects. As such, HPV can also be spread through objects or materials that may have come into contact with the infection. It can also be transmitted via direct contact with cuts and abrasions from an infected individual, and in rare cases, it can be spread during birth via mother-to-child transmission.
Distribution and Seasonality
HPV is present in all climates and seasons.
Immunity
It is unclear whether natural immunity develops after the first infection with HPV. There is evidence that infection with one type of HPV may provide some protection against that one particular type, but it will not provide protection against other HPV types.
Therefore, the HPV vaccine provides immunity and it is an important cancer-prevention tool. The serological response after HPV vaccination is vastly stronger than the response after natural infection, providing people with strong, longterm immune protection to HPV.
Prevention
The best way to prevent HPV is to be vaccinated before starting sexual activity.
According to recommendations from WHO’s Strategic Advisory Group of Experts (SAGE) on immunization and PAHO’s Technical Advisory Group (TAG) on Vaccine-preventable Diseases, the primary target population for vaccination is girls aged 9-14 years before they become sexually active. PAHO/WHO currently recommends that this target group undergo a two-dose schedule with at least six months between doses.
Three safe and effective vaccines are pre-qualified by WHO and two of them are used for most of the countries in the Region to protect against the most harmful strains of HPV, providing strong, long-term immunity. At a population level, high vaccine coverage in girls (>80%) significantly reduces the risk of HPV infection in boys. The vaccine recipient must receive all recommended doses of the vaccine.
The use of condoms correctly during every sexual encounter can help prevent HPV transmission, although HPV can still be spread even when condoms are used.
To prevent cervical cancer, WHO recommends that all women between the ages of 30 to 49 years be screened for cervical cancer at least once by their doctors (even if they have been previously vaccinated against HPV). These screening tests can detect early pre-cancerous changes in the cervix, which can then be treated safely before cervical cancer develops.
WHO: Vaccine Position Papers HPV
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