A single dose of human papillomavirus (HPV) vaccine appears to protect against the infection that causes most cervical cancers as effectively as the standard two-dose regimen, according to results from a large trial in Costa Rica.
HPV is a common sexually transmitted virus; while most infections clear spontaneously, persistent infection with high-risk strains can lead to cervical cancer and a smaller number of head-and-neck and other cancers in both women and men. HPV vaccination has been routinely recommended for girls in the US since 2006, and health authorities are already seeing declines in precancerous cervical lesions among women in their 20s who were vaccinated as adolescents.
Despite this progress, cervical cancer still kills about 340,000 women globally each year, disproportionately affecting low‑ and middle‑income countries where multi-dose vaccination schedules are harder to deliver. Researchers from the US National Cancer Institute and Costa Rica’s Agency for Biomedical Research enrolled more than 20,000 girls aged 12 to 16, randomly assigning them to receive one of two widely used HPV vaccines. Six months later, half received a second dose of the same HPV vaccine, while the others were given an unrelated childhood vaccine, and all participants were followed for five years with regular cervical testing for high‑risk HPV types.
When compared with a separate unvaccinated control group, a single HPV dose provided about 97% protection against infection with the most cancer‑prone HPV strains—similar to the protection achieved with two doses, the investigators reported in the New England Journal of Medicine. Previous studies had hinted that one dose could be sufficient, but this trial confirms strong protection lasting at least five years. In an accompanying editorial, Massachusetts General Hospital infectious disease specialist Dr. Ruanne Barnabas, who was not involved in the study, wrote that the world now has “the evidence and tools to eliminate cervical cancer,” stressing that success depends on implementing vaccination equitably and at scale.
In the US, health authorities currently recommend two HPV doses starting at age 11 or 12 for most girls and boys, with catch‑up vaccination advised up to age 26, in recognition of HPV’s role in multiple cancers beyond the cervix. The Centers for Disease Control and Prevention estimates that about 78% of 13‑ to 17‑year‑olds have received at least one HPV dose. Globally, however, the World Health Organization (WHO) estimates that fewer than one‑third of adolescent girls are vaccinated and has already moved to endorse either one or two doses to make programmes more feasible and expand coverage.
Experts caution that the Costa Rica data only address protection against cervical HPV infections, not other HPV‑related cancers, and that longer-term follow‑up will be critical to confirm durability of single‑dose protection. Even so, the findings are expected to strengthen the case for simplified, one‑shot HPV vaccination strategies in resource‑limited settings as part of global efforts to reduce the burden of cervical cancer.
