In a recent study posted to the Preprints with The Lancet SSRN server*, researchers compared the variation in coverage of the Human Papilloma Virus (HPV) vaccine across 84 countries and its impact in lowering the burden of cervical cancer by analyzing the equity impact of the vaccine on the lifetime projections of the disease among the many cohorts vaccinated between 2010 and 2022.
Equity Impact of Human Papillomavirus Vaccination on Lifetime Projections of Cervical Cancer Burden Amongst Vaccinated Cohorts of 2010-2022 in 84 Countries: Modelling Study. Image Credit: 89stocker / Shutterstock
*Necessary notice: Preprints with The Lancet / SSRN publishes preliminary scientific reports that aren’t peer-reviewed and, due to this fact, shouldn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.
Background
Cervical cancer is among the many five most prevalent cancers amongst women and in addition considered one of the key causes of cancer mortality, with statistics from 2020 reporting over 600,000 recent cases and shut to 350,000 deaths worldwide. In about 36 countries, it’s related to essentially the most significant variety of cancer mortalities, with low- and middle-income countries having the very best burden of cervical cancer.
Currently, there are six approved vaccines against HPV, with one nonavalent, two quadrivalent, and three bivalent vaccines. Some are effective against essentially the most prevalent cancer-causing genotypes, while others are more practical against the high-risk HPV genotypes. Based on various clinical trials, the World Health Organization (WHO) has modified its HPV vaccine dosing regimen since its introduction in 2006, with the present recommendations consisting of a single or two-dose regimen for women between the ages of nine and 14 years and ladies between the ages of 15 and 20 years, and a two-dose regimen for girls over the age of 21 years.
In the current study, the researchers examined the variation in HPV vaccine coverage across countries and its impact in reducing the burden of cervical cancer. The worldwide strategy by the WHO to eliminate cervical cancer consists of achieving 90% vaccination coverage amongst girls approaching 15 years of age, 70% vaccine coverage and 90% treatment coverage for precancer lesions amongst women between the ages of 35 and 45 years, and 90% treatment coverage for girls diagnosed with cervical cancer.
The researchers analyzed the lifetime projected burden of cervical cancer among the many cohorts of ladies vaccinated between 2010 and 2022 across 84 countries to grasp the inequities within the coverage of the HPV vaccine and cervical cancer burden. Despite directives from the WHO, the implementation of the vaccination programs has varied across countries because of political, economic, socio-behavioral, and cultural aspects.
The vaccination impact was assessed by determining the reduction within the variety of cases and deaths and the disability-adjusted life years averted, for which the researchers estimated the decrease within the prevalence, incidence, and mortality of age-specific cervical cancer cases which can be in direct proportion to the efficacy and coverage of HPV vaccines, and the distribution of the high-risk genotypes HPV16/18.
The national immunization coverage estimates from the WHO and the United Nations Kid’s Fund (UNICEF) were used for the analyses, and the study included estimates from 41, 26, 13, and 4 high-, upper-middle, lower-middle and low-income countries, respectively. Concentration indices and curves were calculated to find out the equity impact of the HPV vaccine across these countries.
Results
The findings reported stark inequities within the coverage of HPV vaccine across the 84 countries, with the health impact starting from Switzerland to Tanzania at 4 to 47 cases, two to 34 deaths, and 40 to 735 disability-adjusted life years averted for each 1000 vaccinated girls below the age of 15. The concentration index for the typical coverage distribution across the 84 countries between 2010 and 2022 was 0.33.
Countries with a relatively higher burden of cervical cancer and, consequently, a more significant requirement for HPV vaccination showed a lower HPV vaccination coverage for the 12 years. Furthermore, a big proportion of the countries with the very best burden of cervical cancer haven’t yet included the HPV vaccine of their immunization programs. Of the 194 member countries of the WHO, 60 countries are yet to incorporate the HPV vaccine of their immunization programs.
Despite the HPV vaccine being available since 2006, the shortage of adequate vaccine coverage and implementation highlights the hurdles to fair and equitable access to vaccines in countries within the lower income groups. Nevertheless, the most recent recommendations from the Strategic Advisory Group of Experts (SAGE) of the WHO, which reported comparable protection levels between the one and two-dose regimens for adolescent girls, might reduce most of the challenges to achieving equitable HPV vaccine coverage in these countries.
Moreover, vaccine supply has also been projected to extend, coupled with the most recent SAGE recommendations, could help increase vaccine coverage in countries that have already got incorporated the HPV vaccine of their immunization programs, and potentially extend to countries with no current HPV vaccination programs.
Conclusions
Overall, the study reported that the coverage of HPV vaccination stays highly inequitable the world over, with the countries with the very best burden of cervical cancer having the bottom coverage. Nevertheless, the projected increase in vaccine supply and the most recent recommendations from WHO SAGE for one-dose vaccination regimens are expected to contribute to lowering this inequity.
*Necessary notice: Preprints with The Lancet / SSRN publishes preliminary scientific reports that aren’t peer-reviewed and, due to this fact, shouldn’t be considered conclusive, guide clinical practice/health-related behavior, or treated as established information.