Background Information:
HPV is the most common viral infection of the reproductive tract and causes a range of conditions in men and women, including precancerous lesions that may progress to cancer. While the majority of HPV infections are asymptomatic and resolve spontaneously, persistent infection with HPV may result in disease. In women, persistent infection with oncogenic (cancer causing) HPV types may lead to cervical intraepithelial neoplasia (CIN) which, if untreated, may progress to invasive cervical cancer. In addition, in both men and women, HPV infection is associated with cancers of the head, neck, oropharynx and anogenital area, as well as with anogenital warts and respiratory papillomatosis.
It was estimated that, globally, 91% of HPV-related cancers in women in 2018 were cervical cancers. Cervical cancer was the fourth leading cause of cancer and cancer deaths in women in 2020, with an estimated 604 000 new cases and over 340 000 deaths (8% of all female cancer deaths). HPV16 and HPV18 together are
responsible globally for 71% of cases of cervical cancer. HPV45 accounts for 6%, HPV31 for 4%, HPV33 for 4%, HPV52 for 3% and HPV58 for 2% of cervical cancer cases. Together, these 7 HPV types account for approximately 90% of the squamous-cell carcinomas that are positive for HPV DNA.
Key Messages:
HPV infection is spread through contact with infected genital skin, mucous membranes or bodily fluids, and can be transmitted through sexual intercourse, including oral sex. Most HPV infections (70–90%) are asymptomatic and resolve spontaneously within 1–2 years.
Persistent infection with high-risk types may progress to precancerous lesions which, if not detected and treated appropriately, can progress to invasive carcinoma at the site of infection. Persistent HPV infection, defined by the presence of type-specific HPV DNA on repeated clinical biological samples over a period of time (usually 6 months) is a necessary precursor to cervical cancer.
About 5–10% of all infected women develop persistent infection, which in the cervical site may progress within months or years to premalignant glandular or squamous intraepithelial lesions, classified histopathologically as CIN, and to cancer. Most low grade (1 and 2) CIN lesions regress spontaneously.
The interval between the acquisition of HPV infection and progression to invasive carcinoma is usually 15–20 years or longer.
All HPV vaccines are indicated for use in females aged 9 years or older, and are licensed for use up to 26 or 45 years of age. Some HPV vaccines are also licensed for use in males.
WHO Position
The priority purpose of HPV immunization is the prevention of cervical cancer, which accounts for 82% of all HPV-related cancers.
HPV vaccines should be introduced as part of a coordinated and comprehensive strategy to prevent cervical cancer and other diseases caused by HPV. HPV vaccination is a primary prevention intervention and does not eliminate the need for screening later in life, since the existing vaccines do not protect against all high-risk HPV types and will have limited impact on disease in unvaccinated women and those vaccinated at older ages.
It is not necessary to screen for HPV or HIV infection prior to HPV vaccination.
The primary objective of HPV programmes is to achieve the highest possible population protection among girls by the time they reach 15 years of age; multiple opportunities should therefore be provided for girls to receive their HPV vaccine doses.
Catch-up vaccination of MACs of girls aged between 9 and 18 years at the time of introducing the HPV vaccine results in faster and greater population impact, as a result of increased direct and herd protection. This approach is cost-effective, offers opportunities for economies of scale in delivery and makes programmes more resilient to any interruptions in vaccination.
For the prevention of cervical cancer, the WHO-recommended primary target population for HPV vaccination is girls aged 9–14 years before they become sexually active. HPV immunization programmes should prioritize high coverage from the time of introduction. Achieving over 80% coverage in girls also reduces the risk of HPV infection for boys.
Vaccination of secondary target populations, e.g. females aged ≥15 years, boys, older males or MSM, is recommended only if this is feasible and affordable, and does not divert resources from vaccination of the primary target population or effective cervical cancer screening programmes.
Two-dose schedule. The current evidence supports the recommendation that a 2-dose schedule be used in the primary target group from 9 years of age and for all older age groups for which HPV vaccines are licensed. The minimum interval between first and second dose is 6 months.
WHO now recommends:
- A one or two-dose schedule for girls aged 9-14 years
- A one or two-dose schedule for girls and women aged 15-20 years
- Two doses with a 6-month interval for women older than 21 years
Schedule for Immunocompromised persons. Individuals known to be immunocompromised or HIV-infected (regardless of age or antiretroviral therapy status) should receive at least two HPV vaccine doses (minimum 6 months interval) and, where possible, three doses.
Current evidence suggests that, from a public health perspective, all currently licensed bivalent, quadrivalent and nonavalent vaccines offer comparable immunogenicity, efficacy and effectiveness for the prevention of cervical precancer and cancer, which is mainly caused by HPV types 16 and 18.
HPV vaccines are safe and well tolerated and can be used in persons who are immunocompromised or HIV infected. Adverse events following HPV vaccination are generally mild and of short duration. HPV vaccines should not be given to anyone who has experienced a severe allergic reaction after a previous HPV vaccine dose, or to a component of the vaccine. Data on the safety of HPV vaccination in pregnancy are reassuring but limited. In the absence of well controlled studies in pregnant women, as a precautionary measure vaccination with HPV vaccine is not recommended in pregnancy. If pregnancy occurs following the first dose of vaccination, the subsequent dose should be delayed until after the pregnancy.
Breastfeeding is not a contraindication for HPV vaccination. To prevent syncope,
vaccinees should be seated and observed for 15 minutes following administration of HPV vaccine.
Useful Links:
Link to the new WHO position paper on HPV vaccination:
https://www.who.int/publications/i/item/who-wer9750
Link to WHO page on HPV vaccine:
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