According to findings of two investigations published Online First in The Lancet Oncology, the bivalent human papillomavirus (HPV) vaccine (GlaxoSmithKline, Cervarix) provides exceptional protection against the more serious immediate precursor to invasive cervical cancer (ICC). It is particularly effective in protecting young girls prior to becoming sexually active. The studies reveal that the HPV vaccine also partially protects against 4 other cancer-causing HPV types, which are not targeted by the formulation. These types, together with HPV16/18, are responsible for approximately 85% of cervical cancer globally.

One of the lead researchers, Matti Lehtinen from the University of Tampere in Finland, said:

“Provided that organized vaccination programs achieve high coverage in early adolescents before sexual debut, HPV vaccination has the potential to substantially reduce the incidence of cervical cancer, probably allowing modification of screening programs… when conducted alongside vaccination strategies.”

The vaccine targets HPV types 16 and 18 that cause approximately 70% of cervical cancers. The majority of investigations researching the effectiveness of the vaccine have primarily focused on prevention of cervical intraepithelial neoplasia 2 (CIN2) or higher. Although, it is generally believed that CIN3 is more reproducible and predictive endpoint than CIN2, and frequently progresses to invasive cervical cancer.

In 2009, the largest investigation of HPV16/18 vaccine efficacy to date (the PApilloma TRIal against Cancer In young Adults [PATRICIA]) revealed that the vaccine was highly effective against the pre-cancerous cervical lesions CIN2+.

Nearly 20,000 healthy women aged between 15-25 years from 14 countries in Europe, North America, Latin America and Asia-Pacific participated in the investigation. The participants were randomly assigned into two groups. One group received the HPV vaccine and one group (control) received the hepatitis A vaccines, vaccines were given in three doses at enrollment, 1 month and 6 months.

After 4 year of follow-up, the investigators report on the final examination that evaluated the effectiveness of the vaccine against the early development of adenocarcinoma (AIS), high-grade cervical precanncers (CIN3+), as well as 12 other cancer-causing HPV types not targeted by the vaccine.

Results revealed that the HPV vaccine was 93% effective in protecting young women not already infected with HPV against CIN3+, and prevented 100% of AIS regardless of HPV type in comparison with almost 46% efficacy against CIN3+. The vaccine also protected 77% of the general population of women against AIS. The vaccine prevented 100% of HPV16/18-related CIN3+ among the young women previously unexposed in comparison to almost 46% in the general population regardless of previous exposure to HPV.

According to the researchers:

“Appropriate effectiveness and implementation studies assessing the combination of vaccination and new screening strategies are warranted.”

A second investigation revealed that the vaccine increased cross-protection against other cancer-causing HPV types 31, 33, 51 and 45 in different groups representing diverse groups of women.

Cosette Wheeler from the University of New Mexico Health Sciences Center, Department of Pathology, in the USA, one of the lead authors of the investigation, explains:

“There is a particularly high risk of HPV-33 infections progressing to cervical lesions, and HPV-45 is over-represented in adenocarcinoma…Our results show that cross-protective efficacy might provide substantial additional protection against cervical cancer beyond protection conferred against HPV-16/18.”

In a joint comment, Mark Schiffman and Sholom Wacholder from the National Cancer Institute, Rockville, MD, USA, state:

blockquote> “We believe that increasing coverage, particularly of sexually-naïve adolescent females, is now the most important public-health issue in HPV vaccination efforts.

We are particularly concerned about low vaccination rates in areas where cervical cancer incidence and mortality are high because of inadequate alternative prevention through effective cervical screening, and where nine of 10 cervical cancers deaths occur…The current vaccines are too expensive and difficult to deliver for many low-resource regions.”

Written by Grace Rattue