A randomized controlled trial of 2,275 women in Kenya showed that a single dose of the Human Papillomavirus (HPV) vaccine was highly effective. The current standard for women is a three-dose regimen.
“These findings are a game-changer that may substantially reduce the incidence of HPV-attributable cervical cancer and positions single-dose HPV vaccination as a high value and high impact public health intervention that is within reach for us,” said Kenya Medical Research Institute (KEMRI) Acting Director-General, Prof. Sam Kariuki.
Efficacy of the HPV vaccine
Efficacy (KEN SHE) study was conducted by Kenyan researchers Dr Nelly Mugo, Dr Maricianah Onono, Prof. Elizabeth Bukusi, and Dr Betty Njoroge and Ruanne Barnabas, a Professor of Global Health at the University of Washington School of Medicine.
“The single-dose vaccine was highly effective at 18 months for HPV vaccination,” said Dr Barnabas. “The single-dose efficacy was the same as multiple doses, ” she added.
She intimated that the KEN-SHE trial could help the World Health Organization (WHO) reach its goal to have 90 per cent of 15-year-old girls vaccinated against HPV by 2030.
She said a single-dose vaccine would simplify logistics and decrease costs. Currently, just 15 per cent of women are vaccinated, according to an analysis published March in Preventive Medicine, which outlined a course of action to eliminate the disease.
Like many African countries, the Kenya HPV vaccine program rollout has faced the challenges of vaccine delivery, low uptake of the second HPV dose coupled with global HPV vaccine shortages.
According to Prof. Kariuki, “a single-dose HPV vaccination schedule could alleviate financial and logistical barriers that we currently face. KEMRI will work closely with the Ministry of Health and the researchers in the translation of these findings into action and ensuring that every girl and a young woman get this single shot.”
HPV vaccine trials
In the trial, adolescent girls and young women 15 to 20 years old were randomly assigned therapy and followed from December 2018 to June 2021:
After 18 months, the bivalent vaccine was 97.5 % effective against HPV 16/18 and the nonavalent vaccine was 97.5 % effective against HPV 16/18. The nonavalent vaccine was 89 per cent effective against HPV 16/18/31/33/45/52/58.
Even if women tested positive for one strain of HPV, the vaccine protected them from other strains of the virus.
The majority of participants (57 %) were between 15 and 17 years old and most reported one-lifetime sexual partner (61%).
To be eligible, participants needed to be sexually active, have no more than five-lifetime partners, be HIV-negative, and have no history of HPV vaccination.
More studies to be done
Researchers said more studies need to be done to test how long the vaccine lasts.
“This trial brings new energy to the elimination of cervical cancer. It brings great hope to the women living in countries like Kenya, who have a high burden of the disease,” said Dr Mugo, a senior principal clinical research scientist with the Center for Clinical Research at the Kenya Medical Research Institute in Nairobi.
According to the WHO, most sexually active women and men will be infected with HPV at some point in their lives and some will be repeatedly infected. The peak time for acquiring infection among both women and men is shortly after becoming sexually active.
While nine out of 10 HPV infections go away by themselves in two years, others lead to cancer of the reproductive system, mainly cervical cancer. HPV also can cause cancers of the cervix, vagina, vulva, penis, and oropharyngeal cancer (throat, tongue, and tonsils).
Worldwide, cervical cancer kills women every two minutes, according to the WHO Director-General Dr Tedros Ghebreyesus.