A cancer-causing HPV type found in Nigerian women remains outside the types directly targeted by widely used HPV vaccines, drawing renewed attention to how countries choose products for cervical cancer prevention.
The issue surfaced at WHO’s October 13 vaccine briefing, when a journalist asked about HPV35 and its importance in sub-Saharan Africa. Dr Kate O’Brien, WHO’s immunisation director, said countries should consider the virus types circulating locally when deciding both which vaccine to use and how many doses to give.
“It’s not only about the schedule; it’s also about product decisions,” she said.
The discussion comes as WHO’s vaccine advisers strengthen support for single-dose vaccination and outline options to extend it to younger girls and older women. Wider access addresses one gap in protection; differences between vaccine products raise another.
A 2025 Nigerian study examined high-risk HPV in 189 women with cervical cancer, using samples from a cohort followed between 2018 and 2022. The researchers detected high-risk HPV in 122 women.
Among those positive cases, HPV16 and HPV18 were the most frequently identified types, accounting for 67.2%. HPV35 was detected in 6.6%, alongside other high-risk types including HPV45 and HPV52.
The authors estimated that the types targeted by the four-type vaccine used in Nigeria covered 67.2% of the high-risk infections detected, compared with 86.1% for a nine-type vaccine. These are estimates of type coverage in a particular cancer cohort, not measurements of national vaccine effectiveness or the proportion of all Nigerian cancers that vaccination would prevent.
The researchers called for broader vaccine coverage. Their findings also show why genotype information matters: knowing that HPV is present is different from establishing which types are involved.
Gardasil 9 directly targets nine HPV types: 6, 11, 16, 18, 31, 33, 45, 52 and 58. HPV35 is not among them. Moving to that product would broaden direct protection against several cancer-associated types, but would not add an HPV35-specific component.
That gap does not mean existing vaccines lack value in Africa. HPV16 and HPV18 remain major contributors to cervical cancer in the Nigerian study, and both are targeted by current vaccines. The research concerns how much additional protection could be achieved, alongside efforts to vaccinate more girls.
Earlier research in Ibadan compared HPV patterns in 932 women from the general population with those in 75 women with invasive cervical cancer. It illustrates why the frequency of a type in community samples must be distinguished from its contribution to cancer. Detecting an infection does not establish that it will progress to disease.
In that study’s community sample, HPV35 and HPV16 were equally frequent among women who tested positive for HPV, each detected in 12.2%. That is a finding from a particular place and period, rather than a current national estimate. Comparing community infections with tumour samples helps researchers assess which types are disproportionately associated with cancer.
O’Brien also discussed cross-protection, where a vaccine may offer some protection against types it does not directly target. She said the potential for this protection should be considered when countries move to one dose. The briefing did not quantify protection against HPV35 or announce a vaccine specifically targeting it.
The distinction between direct coverage and possible cross-protection is relevant to purchasing decisions. Countries have to weigh evidence for each product alongside affordability, supply and the number of people their programme can reach.
Screening remains necessary because vaccination does not cover every cancer-causing HPV type or treat existing infection. WHO’s screening recommendations generally start at age 30, and at 25 for women living with HIV. HPV-based screening can detect high-risk infection and guide further assessment before cervical abnormalities develop into invasive cancer.