Table 2. Characterization of upstream and downstream determinants.

Determinant	Definition	Promotion of Determinants	Inhibition of Determinants	Illustrative Quotes Quotes
Upstream Determinants
Financing	Financial considerations (e.g. vaccine pricing, cost of delivery, economic burden, human resources, vaccine cost compared to screening, etc.) that can serve as facilitators or detractors to introduction or scale-up.	Availability of financing through global partners such as Gavi facilitates introduction.	Limited budgets decrease the prioritization of HPV vaccines and can influence delivery selection	“One of the greatest challenges is really in [financing]. You can look at this either on the supply side on the demand side. And on the supply side, one of the greatest issues has really been with having the financial capacity to be able to introduce the vaccine.” Academic Researcher
Vaccine Prioritization	Factors influencing stakeholder prioritization of HPV vaccines, including political commitment and buy-in, relevant data points, and vaccine impact.	The availability of strong data can endorse strong political commitment. This in turn accelerates vaccine prioritization and introduction.	The lack of political will and data serves as a deterrent for vaccine introduction and hinders the creation of immunization policy.	“If you just look at what other certain things in health that were deprioritized the past few years with COVID…the HPV program was already deprioritized…women and girls health has been deprioritize in the past two years. If you’ve got only one team trying to deliver multiple agendas, it makes sense that something’s got to drop.” Global Immunization Partner
Vaccine Supply and Demand	Availability of vaccines globally and how vaccine supply can influence subsequent vaccine introduction and scale-up in LMICs.	Countries are more likely to introduce and meet coverage rates with adequate supply.	Supply deficits cause significant delays to country introduction. For countries that have already introduced, limited supply can impact delivery strategies (i.e. single age cohort v.multi age cohort vaccination)	“… because of the global supply crisis, some of the LMICs withheld introduction of the vaccine for one year, I know some of the countries are waiting for more than two years. So that is another challenge…” Global Immunization Partner
Capacity and Delivery	The state of health systems, human resources, immunization programming and delivery, and monitoring and evaluation of program impact which can influence vaccine introduction and scale-up of HPV vaccines.	Sufficient capacity and effective delivery strategies to reach in-school and out-of school adolescent girls underpins reaching coverage targets.	Inefficient capacity to deliver vaccines (e.g. health system, human resources, cold chain) leads to demotivation for vaccine introduction and suboptimal coverage.	“We’re trying to ask countries to routinize, the HPV vaccine…that it becomes part of the routine program and is readily available. Due to the infrastructure and characteristics of the health system, it may be more optimal for them to deliver the HPV vaccine, like a campaign every few years, and just get all the girls at once.” Global Immunization Partner
Vaccine Accessibility, Equity, and Ethics	Access to HPV vaccines for communities at-large including vulnerable populations, and the right for individuals to be protected and equipped with information pertaining to vaccination including risks and benefits.	Enhancing accessibility, equity, and ethics contributes to promoting vaccine awareness and acceptability and reducing hesitancy.	Introducing vaccines without developing strategies to promote accessibility and equity contributes to low community buy-in resulting in low uptake.	“A lot of studies have been done within the African context, to understand the level of hesitancy when it comes to the HPV vaccination program. It’s difficult to actually measure to quantify…the challenge comes in can you really say that a population is hesitant to a vaccine that actually is not available in their context, when they don’t know about it, when there’s a lack of awareness?” Academic Researcher
Downstream Determinants
Vaccine Acceptability and Hesitancy	Delays in the acceptance or refusal of vaccines despite the potential availability of vaccine services among communities.	Increasing acceptability through vaccine advocacy, dispelling misinformation, and providing platforms for knowledge dissemination reduces hesitancy.	The lack of strategies to mitigate hesitancy in vaccine introduction results in low uptake.	“I think the bigger problem we’ve been facing now is how social media can really push in a whole sorts of information that are not factual about vaccines. For some reason, I think people tend to be taken with more negative sentiments than positive sentiment…the issues still remain much bigger than maybe it’s being addressed.” Academic Researcher
Communications, Advocacy, and Social Mobilization	Efforts to disseminate information pertaining to HPV vaccines, and involve communities in developmental activities that support HPV vaccine introduction	Engagement with trusted leaders to promote advocacy and funding for communications efforts is instrumental to generating community acceptance.	Diminished funding for communications efforts can result in an increase of misinformation once vaccines are introduced.	“We are finding that over time as it seems that the social mobilization, this campaigning, and advocacy starts to dwindle, and that creates challenges. Because it encourages misinformation if the right information is not easily accessible to those who need to find them.” Academic Researcher