Mathematical Model Shows Path to Eradicating Cervical Cancer

Researchers from the University of Maryland have developed an innovative mathematical model capable of determining optimal strategies for the complete elimination of cervical cancer. The results of the work, published in the Bulletin of Mathematical Biology, open new perspectives in the fight against the fourth most common type of oncology among women.

Scale of the Problem

Cervical cancer remains a serious threat to global health. Each year, medical professionals register over 660,000 new cases of this disease. Virtually all of them are associated with the human papillomavirus (HPV) – the most common sexually transmitted infection. The paradox of the situation is that in 90% of cases, the body manages to cope with the virus within two years, but the remaining 10% of cases of persistent infection can lead to the development of cancer.

“The study clearly demonstrates how science influences policy,” noted lead author Abba Gumel, a distinguished professor of mathematics at the University of Maryland, who also works at the Institute of Computational Health Sciences and the Institute of Physical Sciences and Technology.

South Korean Case

To test their model, the scientists chose South Korea – a country with a developed healthcare system and accessible statistical data. The model takes into account numerous factors: gender, vaccination status, presence of HPV infection, and stage of disease development. Calibration was based on cancer incidence data from 1999 to 2020.

South Korea's national immunization program, launched in 2016, covers approximately 80% of girls aged 12-17. Additionally, 30,000 women aged 18-26 receive what is known as “catch-up vaccination” annually. The national screening program provides regular Pap tests for 61% of Korean women over 20 years old.

However, modeling revealed the inadequacy of current measures. “This allows for achieving the goal of reducing cervical cancer cases, but it will not eradicate it completely,” explained Gumel, who collaborated with a team of HPV vaccine developers from Merck Inc. – “The goal is eradication.”

Two Paths to Success

The research group proposed two realistic scenarios for achieving complete elimination of the virus in South Korea. The first option involves expanding vaccination coverage to 99% of the female population. The second scenario maintains the current level of 80% for girls but adds vaccination for 65% of boys aged 12-17.

“Vaccinating boys reduces the burden associated with the need to vaccinate a significant portion of girls,” explained Gumel, who holds the Michael and Eugenia Brin Chair in Mathematics. “This makes disease eradication more realistic.”

According to calculations, the first scenario would eradicate HPV-associated cancers within 60 years, while the second would do so in 70 years. Soen Pak, the lead author of the study and a graduate student in applied mathematics and statistics, emphasized the realism of both strategies for Korea, considering that childhood immunization coverage against measles in the country reaches 98%.

“The level of vaccine hesitancy is very low,” added the researcher.

Herd Immunity as a Goal

Both proposed solutions aim to achieve herd immunity – a state in which individuals unable to receive the vaccine for medical reasons will be protected due to the high level of vaccination among those around them.

“The way to protect them is to surround them with a sea of immunity,” Gumel metaphorically expressed.

Interestingly, modeling showed limited effectiveness of expanding screening programs. Increasing the coverage of Pap tests would provide only minimal additional benefit. In contrast, strategies aimed at promoting safer sexual practices, including condom use, demonstrated high effectiveness in reducing the spread of HPV and related cancers.

Expanding the Model

Pak continues to refine the mathematical model by incorporating the dynamics of contacts among men who have sex with men, as well as other high-risk groups, such as women engaged in prostitution. Such expansion will make the model even more accurate and applicable to various social contexts.

At a conference in South Korea last year, the researcher met with colleagues closely collaborating with Korean health authorities. They showed significant interest in using the results of the work to optimize the national disease prevention program.

Global Application

The developed model is not limited to one country. Researchers emphasize its universality and potential for application in various regions of the world, including the USA.

“We could use other data to compare the lessons learned from the fight against HPV with the experience of the USA,” reflects Pak. “Can we do the same? Will the same intervention strategies work effectively here?”

Gumel is optimistic about the prospects of applying the model in the American context. He believes that using the Gardasil-9 vaccine, which has an efficacy of up to 95% and is available in the USA, achieving herd immunity would require coverage of about 70% of the target population.