[Evaluation of bilateral vaccine cooperation priority countries on Chinese human papillomavirus vaccine using hierarchical K-means hybrid clustering].

OBJECTIVE: To evaluate priority target countries and formulate context-specific cooperation modalities for China ' s bilateral international collaboration on human papillomavirus (HPV) vaccines, thereby furnishing an evidence-based reference for optimizing China ' s bilateral vaccine cooperation stra-tegies and contributing to global health equity.

METHODS: Using a previously established index system designed for selecting preferred countries in China ' s international vaccine cooperation, we comprehensively applied a weighted-scoring approach to quantitatively rank 29 Phases 3 and 4 Global Alliance for Vaccines and Immunization (Gavi) eligible countries in HPV vaccine cooperation. Based on 5 first-level index (legal and regulatory factors, economic factors, political factors, social factors, and technological factors) scores, a hierarchical K-means hybrid method was used for clustering the countries. Hierarchical clustering was initially utilized to explore the underlying data structure and determine the optimal number of clusters, followed by K-means clustering to precisely categorize the evaluated nations based on their multidimensional characteristics.

RESULTS: The top10 countries were mostly Asian countries. African countries were mostly in the lower ranks. The countries were clustered into three types: (1) Technology transfer priority (n=3: Indonesia, Viet Nam, Uzbekistan), characterized by above-average economic, techno-scientific and political scores, robust vaccine-import volumes, non-negligible domestic manufacturing capacity and high political stability-recommended for priority collaboration; (2) Basic assistance (n=25), approximating mean indicator values, typically low-population or low-income economies suitable for aid-based or concessional-procurement models; (3) High barrier (n=1: India), exhibiting high socio-demographic and scientific base yet minimal legal-regulatory scores, indicating large demand, established vaccine industry, but formidable registration barriers. Policy recommendations included: concessional product export plus clinical-trial cooperation with Indonesia, with prospective licensing and technology transfer; clinical-trial collaboration with Viet Nam; and licensing/technology-transfer schemes with Uzbekistan.

CONCLUSION: Indonesia, Viet Nam, and Uzbekistan are identified as the priority target countries for China ' s bilateral international cooperation on HPV vaccines. For these technology-transfer priority nations, cooperation should be strategically conducted through diverse modalities encompassing vaccine product export, clinical trial collaboration, authorized licensing, and technology transfer.