Experts consider single-dose HPV vaccine as new evidence challenges traditional two-dose schedule

Medical experts in the US are debating the potential shift to a one-dose HPV vaccination regime for children and teenagers, as emerging evidence questions the necessity of the current two-dose approach amid ongoing policy and political tensions.

Medical experts are weighing a major change to one of the most widely used cancer-prevention vaccines: whether a single dose of the HPV jab may be enough for some children and teenagers. For years, doctors have urged parents to complete a two-dose schedule, but new evidence is pushing researchers and health groups to reconsider that advice as vaccination policy in the United States becomes increasingly fractured.

Jason Schwartz, a vaccine policy researcher at Yale University, told The Associated Press that a move to one dose would amount to a significant change in what families have been told for years about protecting adolescents against human papillomavirus, or HPV. The discussion comes at a moment when federal health policy has been unsettled, with the government and leading medical organisations clashing over childhood vaccination guidance.

HPV is the most common sexually transmitted infection in the United States and is linked to a large share of cancers affecting the cervix, anus, mouth, throat and other genital tissues. Public health authorities say it contributes to nearly 50,000 cancer diagnoses a year in the US, and the Centres for Disease Control and Prevention has estimated that about 90% of cervical and anal cancers are caused by HPV infection. The vaccine was first approved in 2006, and doctors have long urged families to vaccinate early, ideally at ages 11 or 12, before exposure to the virus. The American Cancer Society says that vaccination between ages 9 and 12 offers the best protection.

HPV vaccination guidance has already changed once in a major way. The original recommendation called for three doses, then was cut to two a decade ago after studies showed that two shots gave strong protection when spaced several months apart. Since then, evidence from multiple countries has pointed to steep declines in HPV infections, genital warts and precancerous cervical changes among vaccinated groups. The American Cancer Society updated its cervical screening advice in 2020, raising the recommended start age to 25 from 21, citing the effect of vaccination on early signs of cancer.

The case for a simpler schedule has strengthened in recent years. A review published by the University of Minnesota’s Vaccine Integrity Project found that HPV vaccines lower the risk of cancers in the genital area among women. Research published in JAMA Oncology in April found vaccinated males were nearly 50% less likely to develop cancers of the head and neck, oesophagus, anus or penis. Angela Ulrich, who led the review, told the project that protection appears to last for decades. At the same time, the National Institutes of Health has highlighted research suggesting that one dose can perform similarly to two in protecting against HPV, and the National Cancer Institute says evidence now supports the idea that a single shot can provide meaningful protection against the virus.

Still, experts caution that the evidence is not yet complete for every group. A Costa Rica study last year tracking more than 20,000 girls over five years found that one dose offered about 97% protection against cervical cancer, close to the effect of two doses. But researchers say there is less information on whether one dose gives boys enough protection against the wider range of HPV-related cancers they face. For now, medical experts continue to advise two shots. That may change as more data arrive, but the main message from doctors remains unchanged: vaccination matters because it prevents cancer.

The debate has also been shaped by politics and practical concerns. HPV vaccination rates in the US have stalled at about 63% for teenagers receiving both doses, according to recent CDC data, with uptake lagging behind some other adolescent vaccines. Many states do not require HPV vaccination for school entry, and doctors say the shot’s reputation for being more painful than others may also discourage families. Robert F. Kennedy Jr.’s move to order a reduction to one recommended dose earlier this year was blocked by a federal judge, yet the proposal reflected a discussion already under way among specialists and advisory groups before the disruption. The American Academy of Pediatrics, which has sued Kennedy, said it has been reviewing whether one dose may be sufficient for some children and at what age vaccination should begin.