Cervical cancer remains a significant health issue globally, ranking as the fourth most common cancer among women and causing more than 660,000 new cases and nearly 350,000 deaths annually. Researchers at the University of Maryland have developed a mathematical model that could help public health officials design better vaccination and screening strategies to contain and potentially eliminate cervical cancer.
The study, published in the Bulletin of Mathematical Biology, was led by Abba Gumel, Distinguished University Professor of Mathematics at UMD. "The study provides a clear way of showing how science is influencing policy," said Gumel.
Almost all cases of cervical cancer are caused by human papillomavirus (HPV), which is considered the world's most common sexually transmitted infection. Although HPV infections often resolve naturally within two years for most people, persistent infections can lead to cancer. Vaccines against HPV are available in 147 countries and can reduce both disease spread and cancer risk.
Using demographic and epidemiological data from South Korea between 1999 and 2020, the UMD team built a model that predicts HPV transmission across different population groups based on sex, vaccination status, infection status, and progression to cancer. The model allows for testing various vaccination strategies over time.
Findings indicate that current efforts in South Korea—including vaccinating about 80% of girls aged 12-17 through the National Immunization Program (NIP) since 2016—will lower but not eliminate HPV-related cancers. About 30,000 women aged 18-26 also receive catch-up vaccinations each year. Additionally, around 61% of Korean women over age 20 receive regular Pap tests under the National Cancer Screening Program.
"It's achieving the objective of reducing cases of cervical cancer, but it's not going to eliminate it," said Gumel. "The objective is elimination."
The researchers identified two scenarios that could achieve elimination: expanding vaccine coverage to include 99% of females or maintaining current female coverage while vaccinating 65% of boys aged 12-17. According to simulations using their model, these strategies would eliminate HPV-related cancers in South Korea within approximately six or seven decades.
Public acceptance for vaccines in South Korea is high; national infant immunization rates approach 98%. "There's very low vaccine hesitancy," said Park.
"Vaccinating boys reduces the pressure of having to vaccinate a large proportion of females," added Gumel. "It makes elimination more realistically achievable."
Achieving herd immunity through these approaches would protect those unable to be vaccinated due to age or allergies. "The way to protect them is to surround them with a sea of immunity," Gumel said.
While expanding Pap test coverage offers only marginal benefits according to their findings, promoting safer sex practices such as condom use could significantly reduce HPV transmission rates in communities.
Park is currently refining the model further by considering contact patterns among men who have sex with men and other high-risk groups like female sex workers. The research has drawn interest from Korean public health agencies for potential application in improving national immunization policies. Park noted that similar approaches could be tested elsewhere: "We could use different data to compare the lessons learned about HPV to the U.S... Can we do the same thing? Will the same set of intervention strategies work effectively here?"
Gumel pointed out that with highly effective vaccines such as Gardisil-9 available in countries like the United States—where it offers up to 95% protection—achieving about 70% coverage may be enough for herd immunity against HPV.
"We do not have to be losing 350,000 people globally to cervical cancer each year," he said. "We can see an end to HPV and HPV-related cancers if we improve the vaccination coverage."
UMD mathematics Ph.D. candidate Hyunah Lim co-authored this article with Gumel and Park.
