The role of HPV single-dose vaccination in expanding access in GAVI-supported countries during a period of supply constraints
Over 2023 and 2024, 19 of the countries that were supported by Gavi to purchase HPV vaccines adopted a single-dose HPV vaccination schedule. The goal of this study is to estimate the impact on vaccination access and the number of cervical cancers averted compared to a two-dose schedule. We estimated the population that could be targeted in countries supported by Gavi to purchase HPV vaccines. We used UNICEF shipment plans to identify the number of HPV doses shipped to each country in 2023 and 2024, plus information supplied by Gavi on the dose schedule implemented in each country and year, adjusting for vaccine wastage. We computed the number of girls that could have been reached, first assuming complete utilization of all shipped doses under a single-dose schedule, and second assuming a counterfactual scenario where all countries would have used a 2-dose schedule. We then compared this to country-reported data on the number of girls actually vaccinated. For each of the three scenarios we modeled the number of cervical cancers averted using HPVsim, a microsimulation model calibrated to each country. We calculate that the introduction of single-dose HPV vaccination in Gavi-supported countries would have allowed these countries to target 23.3M additional girls if all supply was utilized. Reported data on girls vaccinated indicates that in actuality an additional 18.5M girls were reached due to adoption of single-dose. We estimate that the use of single-dose schedule in 2023 and 2024 could have averted up to 370,000 (356,000-376,000) additional future cervical cancers if all supply had been utilized, and 297,000 (222,000-369,000) given actual utilization. The single-dose HPV vaccination strategy has had a substantial positive impact on cervical cancer elimination in context of supply constraints affecting low and middle-income countries.