Background
Increasing global HPV vaccine supply and single-dose vaccination recommendations stimulate increased debate and willingness for catch-up vaccination of females 15 years or older in lower- and middle-income countries (LMICs). Countries with different epidemiological contexts of HPV prevalence and sexual behaviour of populations would expect different impacts of HPV catch-up vaccination programs.

Objectives
This work aims to provide epidemiological indicators to help guide the complex decisions on HPV vaccination catch-up age in LMICs from both a local perspective (equitable for women in a given jurisdiction), and a global perspective (equitable for women in LMICs world-wide).
 
Methods
123 LMICs were grouped in seven clusters (see map) based on sexual behaviour data or geography. Cluster specific optimal catch-up ages were identified by optimising dose efficiency. Incremental catch-up ages scenarios were explored using the previously validated and publicly available METHIS modelling platform of the Public Health Decision Science Team of IARC, assuming single-dose vaccination with 90% coverage. Country-specific expected health impact and doses needed were estimated for the identified optimal catch-up ages.
 
Results
Two optimum catch-up ages were identified per cluster: local catch-up age (maximum catch-up age with dose efficiency similar to that of the primary target age (9-14 years) locally), and global catch-up age (maximum catch-up age with dose efficiency below a fixed threshold equal for all LMICs).
The local optimal catch-up age ranged from 16 years for Clusters I and II, to 20 years for clusters V and VI. The global optimal catch-up age ranged from 20 years for Cluster VII to 30 years, for Clusters I and II.
If all LMICs implemented catch-up vaccination up to the local (or global) catch-up age, a total of 3.6 million (or 5.2 million) cervical cancer cases would be prevented among birth cohorts aged 11-30 years at vaccination. Approximately 456 million doses would be needed to implement the local catch-up age vaccinations (729 million for catch-up vaccinations up to the global optimal ages).

Conclusions/Implications
From the local perspective, local stakeholders are encouraged to consider at minima catch-up vaccination up to the local catch-up age. Using the global perspective, global stakeholders may seek to shape an ideal globally available vaccine supply and funding.

Map of the 7 LMIC clusters