San José, Costa Rica, April 2025. The first results of the ESCUDO study, conducted in Costa Rica by the Costa Rican Agency for Biomedical Research (ACIB-FUNIN) in collaboration with the National Cancer Institute of the United States, were announced at the annual meeting of the American Association for Cancer Research (AACR), considered one of the most important scientific events in this field worldwide.

The main findings confirm that a single dose of the Human Papillomavirus (HPV) vaccine offers the same protection as two doses against HPV types 16 and 18, which are responsible for more than 70% of cervical cancer cases worldwide.

The two vaccines used in the study demonstrated more than 95% efficacy in preventing HPV 16 and 18 infections, both when administered with one dose and when administered with two doses.

ESCUDDO is the only study worldwide that sought to verify whether the protection provided by one dose of the vaccine was not inferior to the provided by two doses in preventing HPV types 16 and 18 infections. This research, which has been conducted in more than 50 cantons of Costa Rica since 2017, involves more than 20,000 women between the ages of 12 and 20.

The study is supported by the U.S. National Cancer Institute (NCI), the Bill & Melinda Gates Foundation, the NIH Office of Research on Women’s Health, and the International Agency for Research on Cancer.

Global impact: greater access, greater equity

With scientific confirmation that a single dose is just as effective as the traditional two-dose regimen, it opens the door to broader global coverage, especially in low- and middle-income countries, where access to complete vaccination regimens has been limited for economic or logistical reasons.

“Reducing vaccination to a single dose represents a more efficient, accessible, and scalable strategy for saving lives,” said Dr. Carolina Porras, director of biomedical research at ACIB-FUNIN. She also expressed her gratitude to the thousands of young people who participated in the ESCUDDO study, whose contributions made such important findings possible.Principio del formulario

The ESCUDDO results provide robust evidence for regulatory agencies to definitely, change their vaccination recommendation to a single dose. Currently, the WHO recommends administering one or two doses to girls and boys aged 9 to 14, as well as to the 15 to 20-year-old group, leaving the number of doses to governments’ discretion.

“Now, with the results of the ESCUDDO study, the recommendation to administer a single dose is supported by highly scientifically rigorous data, and we know this will be a significant contribution to countries improving their vaccination coverage,” emphasizes Dr. Rolando Herrero, scientific director of ACIB-FUNIN.

ACIB-FUNIN will continue developing the ESCUDDO study in Costa Rica to further evaluate the duration of protection provided by one dose. This Costa Rican non-governmental, non-profit organization has distinguished researchers who, for more than 30 years, have dedicated themselves to conducting biomedical research with a significant impact on global public health.

The full manuscript of this study, currently under preparation, will include detailed analyses of the efficacy of one or two doses against the different types of viruses associated with this cancer, as well as details of the immune response to them.

The AACR Annual Meeting presents the latest discoveries in basic, translational, and clinical cancer research and brings together thousands of experts to share knowledge that will guide the future of the fight against cancer.