Single-dose vaccine delivers protection against cervical cancer-causing HPV comparable to 2 or 3-dose regimes

A recent report published in the World Health Organization (WHO) News Release suggested that a single dose of the human papillomavirus (HPV) vaccination confers equivalent immunity to a two-dose schedule against cervical cancers caused by HPV. 

Background

The WHO Strategic Advisory Group of Experts on Immunization (SAGE), conducted between April 4^th to 7^th, 2022, assessed recent reports indicating that single-dose vaccine regimens are equally effective as two- or three-dose schedules. According to recent studies, the SAGE concluded that a single-dose HPV vaccination provides equivalent protection as a two-dose regimen against HPV, the most common virus causing cervical cancer. Additional doses of the life-saving shot reaching more girls might be a game-changer for disease prevention.

What is cervical cancer?

Cervical cancer develops in the connecting part of the uterus and vagina in women, called the cervix, and is the fourth most frequent cancer in females. Infection with high-risk HPV, an exceedingly prevalent virus spread through sexual contact, is associated with nearly 99% of cervical cancer cases. Although most HPV infections cause no symptoms and resolve spontaneously, persistent HPV infection might lead to cervical cancers. HPV vaccination, screening, and treating precancerous lesions will help prevent almost all cervical cancer cases. Cervical cancer is among the most successfully treated cancers once diagnosed early and managed adequately. Cancers detected in late stages can still be managed with palliative care and the right therapy.

What is HPV?

HPV is a virus that infects the skin and several mucous membranes, like those in the genital area or cervix. There are more than 200 kinds of HPV, which are assigned numbers in the order of their discovery. High-risk HPV types are sexually transmitted and can cause several cancers, including cervical cancer. On the other hand, low-risk HPV kinds can cause verrucae, common warts, and wart-like growths in the airway passages. 

What is an HPV vaccine?

HPV vaccines comprise virus-like particles (VLPs) and other ingredients usually found in vaccines and other pharmaceuticals. The protein coat of the HPV virus and not its genetic material is incorporated into the VLPs with the help of recombinant deoxyribonucleic acid (DNA) technology. The HPV vaccine contains aluminum sulfate, an adjuvant, in small quantities that help enhance the body's immune responses, and also has water and mineral salts, including polysorbate 80, sodium borate, and L-histidine. The three clinically approved HPV vaccines are Gardasil, Cervarix, and Gardasil 9.

The HPV vaccine induces protective antibodies against infection through its HPV-resembling structure. All three approved HPV vaccines protect against the most prevalent cancer-causing strains of HPV. HPV vaccines are nearly 100% effective in preventing future infections with the HPV virus types they contain. Furthermore, since these vaccines do not contain live viruses, they would not induce cancer or HPV infection.

SAGE report on HPV vaccination against cervical cancer

Cervical cancer is frequently referred to as the silent killer and is almost completely preventable. The latest SAGE recommendation about the considerable efficacy of the one-dose HPV vaccination against cervical cancer is based on concerns about the sluggish introduction of the HPV vaccine into immunization campaigns and generally low population coverage, particularly in economically backward nations. About 90% of HPV-induced cervical cancers are commonly reported in women from middle and low-income countries. Existing reports indicate that the HPV immunization is highly potent in preventing HPV serotypes 18 and 16, responsible for 70% of cervical cancers.

SAGE advises all nations to implement HPV vaccinations and make multi-age group catch-up of missed doses and elder groups of girls a top priority. This will help vaccinate more women and girls against HPV and prevent cervical cancer and its complications throughout their lives. The SAGE-recommended updated HPV dose regimens are one- or two-dose regimens for girls aged between nine and 14 years (primary target) and 15- to 20-year-old young women, and two doses administered at a six-month gap in women aged >21 years. 

Since there is no adequate proof of the efficacy of a single-shot HPV vaccine in immunocompromised individuals, they should receive three doses at least two doses of the HPV vaccine. The WHO recommendations for this cohort will be amended following more stakeholder input.

In 2020, the two-dose HPV vaccine global coverage was just 13%. The factors contributing to the low coverage and slow uptake of the HPV vaccine include the expenses associated with two-dose vaccination of older girls who do not come under childhood vaccination campaigns, the comparatively high cost of HPV vaccines, and supply and logistic challenges. During the meeting, SAGE emphasized the need for a political commitment coupled with fair paths for HPV vaccine accessibility. Failure to do so would be an injustice to a generation of young women and girls who might be in danger of cervical cancer.

Conclusions

The recent WHO SAGE meeting to discuss vaccines and immunization reported that a single-shot of HPV vaccination is equally effective as a two-dose regimen in safeguarding women from HPV-induced cervical cancers based on available evidence. The team believed that the single-dose HPV vaccine recommendation might aid the goal to vaccinate 90% of girls aged 15 years against HPV by 2030.

The single-shot regimen of HPV vaccination is easier to administer and less expensive and resource-intensive. Thus, it facilitates launching catch-up vaccination programs for several age groups, avoids the obstacles to locating girls for second-dose vaccination, and frees up human and financial resources to focus on other health issues. 

Written by

Shanet Susan Alex

Shanet Susan Alex, a medical writer, based in Kerala, India, is a Doctor of Pharmacy graduate from Kerala University of Health Sciences. Her academic background is in clinical pharmacy and research, and she is passionate about medical writing. Shanet has published papers in the International Journal of Medical Science and Current Research (IJMSCR), the International Journal of Pharmacy (IJP), and the International Journal of Medical Science and Applied Research (IJMSAR). Apart from work, she enjoys listening to music and watching movies.