A single dose of the human papillomavirus vaccine is highly effective in preventing infection over three years and may reduce the incidence of cervical cancer and other virus-associated diseases, according to a new study in Kenya. Most sexual.
A single-dose strategy would dramatically expand vaccine supply, reduce costs, and simplify its distribution. This could make vaccination a more viable option in countries with limited resources, experts say.
HPV is a sexually transmitted disease associated with cervical cancer and other malignancies. Health authorities in many countries Including UStwo doses are recommended for adolescent girls under the age of 15, and three doses for older girls.
However, observational data have long suggested that a single dose provides effective protection against HPV for at least 10 years. The new results are the first confirmation from a gold standard clinical trial that one dose can be as effective as two or three doses for at least three years.
Results from head-to-head comparisons between single-dose and two-dose regimens will not be available until 2025.
According to the World Health Organization, at least 24 countries, including Mexico, Tonga and Guyana, have moved to a single-dose approach.
New evidence may persuade more countries to adopt the strategy.
“What we predicted was that this would be of most interest to low- and middle-income countries,” said Paul Bloom, senior adviser to the WHO’s HPV vaccination program. But high-income countries like Britain and Australia are the first to change their policies, he pointed out.
WHO states that if widely deployed, a single-dose strategy would be could have prevented Over the next 100 years, 60 million people will develop cervical cancer worldwide and 45 million will die.
cervical cancer 4th most common cancer type in women worldwideAccording to WHO, there were an estimated 604,000 new cases in 2020 and an estimated 342,000 women died from the disease in 2020.
“This is the true killer of women,” said Dr. Seth Barkley, chief executive of Gavi, which funds immunization programs in low-income countries.
“It’s also a disease that really kills women in the prime of life,” he added.
Over 95% of cervical cancers are caused by the sexually transmitted disease HPV. Although multiple viral strains are prevalent, subtypes 16 and 18 account for 70% of cervical cancers.
The HPV vaccine came out in 2006 and is “a near-perfect preventive intervention for cervical cancer and other HPV-related cancers,” said the director of the infectious disease division at Massachusetts General Hospital, who led the new study. Dr. Ruan Barnabas said.
The Food and Drug Administration approved a vaccine in the United States that year, and since then infection with the cancer-causing virus strain fell It’s up more than 80 percent nationally, according to the Centers for Disease Control and Prevention.
Still, about 13,000 Americans are diagnosed with cervical cancer each year. About 4,000 women die from this disease each year.
The burden of HPV is much higher in low- and middle-income countries where women have limited access to cervical cancer screening and treatment. About 90% of cervical cancer deaths in 2020 were women living in resource-poor countries.
In Kenya, the vaccine is currently given twice. But from the age of 9 he is only 33% of girls from the age of 14. receive the first dose, and the second return is only 16%. in contrast, 78% or more Percentage of US adolescent girls who received at least one dose of vaccine in 2021.
Single-dose vaccination regimens are much easier to implement at scale and open up more delivery channels, such as village-wide campaigns and mobile clinics.
Dr. Peter Dall, who leads HPV vaccine development at the Bill & Melinda Gates Foundation, which funded the study, said:
in the Ken Shi StudyResearchers randomly assigned 2,275 Kenyan women aged 15 to 20 years to receive one dose of HPV vaccine targeting subtypes 16 and 18. HPV vaccines targeting 16, 18, and other her 7 subtypes. or meningococcal vaccine as a control.
Scientists took cervical and vaginal swabs from women every six months and looked for HPV infections that persisted up to 36 months.
The vaccine was 98% effective against virus subtypes 16 and 18 and 96% effective against all cancer-causing strains over three years, the study found. I was. No serious side effects have been reported.
Previous research results, published last yearshowed that a single dose of both vaccines was highly effective for 18 months.
Based in part on that evidence, WHO changed its recommendations last year to: 1 or 2 doses Girls and young women between the ages of 9 and 20 and women over the age of 21 receive two doses 6 months apart.
Programs funded by Gavi have so far met only about a third of their goals due to a shortage of vaccine supplies. About 20 million doses were available in 2022, according to Dr. Berkley, but that number is expected to more than triple by 2025.
