Fewer doses of HPV vaccine may be sufficient to protect against cervical cancer

A new study shows that one or two doses of the HPV vaccine can be as effective against severe cervical changes as three doses for girls and young women. The findings could have significant implications for global efforts to eliminate cervical cancer.

A recent study by researchers at Karolinska Institutet, published in The Lancet Regional Health - Europe, indicates that one or two doses of the HPV vaccine given before age 17 provide comparable level of protection against severe cervical changes as three doses. The study is based on data from over 2.2 million Swedish girls and women and has followed the effects of vaccination for up to 17 years.

Our results support the recommendations from the World Health Organization (WHO) that one or two doses could be sufficient to protect girls and young women against cervical cancer."

Shiqiang Wu, research assistant, Department of Medical Epidemiology and Biostatistics, Karolinska Institutet

Cervical cancer is the fourth most common cancer in women worldwide, causing over 340,000 deaths in 2020. The WHO aims to eliminate cervical cancer as a public health problem by the end of the century, with one of its key targets being 90% vaccination coverage among girls before the age of 15.

"Our findings strengthen the evidence that one or two doses of the HPV vaccine may be sufficient, which could help vaccinate more girls and accelerate efforts to eliminate cervical cancer," says Jiayao Lei, assistant professor at the Department of Medical Epidemiology and Biostatistics and the Department of Clinical Science, Intervention and Technology, Karolinska Institutet.

The study is based on data from Swedish national registries, including information on vaccinations and the occurrence of high-grade cervical lesions in women aged 10-35 years during the period 2006-2022. To ensure the results were not influenced by factors such as socioeconomic background and maternal history of severe cervical changes, researchers adjusted for these variables.The results show that young girls who received one or two doses of the HPV vaccine before the age of 17 had a comparable risk of severe cervical changes as those who received three doses.

The research highlights a potential breakthrough in reducing the number of required vaccine doses. However, the researchers emphasize that more studies are needed to understand the duration of protection and whether a booster dose might be necessary in the future.

"The next step is to follow those who received fewer than three doses over a longer period to ensure continued protection against cervical cancer and to study the effects of the new 9-valent vaccine," concludes Jiayao Lei.

The study demonstrates the protective effect of fewer doses and supports reducing the number of doses to make vaccination more accessible globally, particularly in low- and middle-income countries where the burden of cervical cancer is greatest.