A single dose of the human papillomavirus vaccine is very effective in preventing infections for up to three years and is likely to reduce the incidence of cervical cancer and other diseases associated with the virus, according to a new study from Kenya.

A single-dose strategy would greatly expand vaccine supplies, reduce costs and simplify distribution, experts say, making vaccination a more viable option in resource-poor countries.

HPV is a sexually transmitted infection associated with cervical cancer and other malignancies. Health officials in many countries including the United Statesrecommend two doses of the vaccine for adolescent girls under 15 and three doses for those older.

But observational evidence has long shown that a single dose provides effective protection against HPV for at least a decade. The new results are the first confirmation of a gold standard clinical trial that one dose can be as effective as two or three doses for at least three years.

Direct comparison results between single-dose and two-dose regimens will not be available until 2025.

At least 24 countries, including Mexico, Tonga and Guyana, have switched to a single-dose approach, according to the World Health Organization.

New data may convince more countries to adopt this strategy.

“We predicted that it would be most interesting for low- and middle-income countries,” said Paul Bloom, WHO senior adviser on HPV vaccination programs. change their policies, he noted.

WHO estimates that if the single dose strategy is widely adopted can prevent 60 million cases of cervical cancer and 45 million deaths worldwide over the next 100 years.

Cervical cancer fourth most common cancer in women worldwideWHO estimates that there were 604,000 new cases in 2020. An estimated 342,000 women died from the disease in 2020, more than the number who died during pregnancy or childbirth.

“This is a real killer of women,” said the doctor. Seth Berkley, chief executive of Gavi, which funds immunization programs in low-income countries.

“It’s also a disease that really kills women in their prime,” he added, “and does it in a really horrific way.”

More than 95 percent of cervical cancers are caused by HPV, a sexually transmitted disease. Multiple strains of the virus predominate, but subtypes 16 and 18 are responsible for 70% of cervical cancers.

The HPV vaccine debuted in 2006 and is “a near-perfect preventive measure for cervical cancer and other HPV-related cancers,” the doctor said. Ruanne Barnabas, director of infectious diseases at Massachusetts General Hospital, led the new study.

The Food and Drug Administration approved a vaccine the same year in the United States, and infections with cancer-causing viral strains have since been fell more than 80 percent in the country, according to the Centers for Disease Control and Prevention.

Still about 13000 Americans are diagnosed with cervical cancer every year; About 4,000 women die from this disease every year.

The damage from HPV is much greater in low- and middle-income countries, where women have limited access to cervical cancer screening or treatment. Approximately 90 percent of cervical cancer deaths in 2020 were among women living in countries with limited resources.

In Kenya, the vaccine is currently administered in two doses. But only 33 percent of girls aged 9 to 14 get the first dose, and only 16 percent return for a second. against, over 78 percent teenage girls in the US received at least one dose of the vaccine in 2021.

The single shot scheme is much easier to scale up and opens up more delivery channels such as village-wide campaigns and mobile clinics.

“This provides an opportunity to get creative with the delivery mechanism,” said the doctor. Peter Dall, head of HPV vaccine development at the Bill & Melinda Gates Foundation, which funded the study.

V KEN SHE study, researchers randomly assigned 2,275 Kenyan women aged 15 to 20 to receive a single dose of HPV vaccine targeting subtypes 16 and 18; an HPV vaccine targeting 16, 18 and seven other subtypes; or meningococcal vaccine as a control.

The scientists took cervical and vaginal swabs from the women every six months and looked for persistent HPV infection up to 36 months.

The study found that the vaccine was 98 percent effective against subtypes 16 and 18 of the virus over three years and 96 percent effective against all cancer-causing strains. No serious side effects were reported.

Earlier results of the study, published last yearshowed that a single dose of both vaccines was highly effective for 18 months.

Based in part on this evidence, last year the WHO changed its recommendation to one or two doses for girls and young women aged 9 to 20 years and two doses six months apart for women over 21 years of age.

Gavi-funded programs have only reached one-third of their target so far, due in part to a shortage of a vaccine. In 2022, about 20 million doses were available. Berkeley, but this number is expected to more than triple by 2025.