Background: Timor-Leste's immunization coverage is among the poorest in Asia. The 2009/2010 Demographic and Health Survey found that complete vaccination coverage in urban areas, at 47.7%, was lower than in rural areas, at 54.1%. The city of Dili, the capital of Timor-Leste, had even lower coverage (43.4%) than the national urban average.

Objective: To better understand the service- and user-related factors that account for low vaccination coverage in urban Dili, despite high literacy rates and relatively good access to immunization services and communication media.

Methods: A mixed-methods (mainly qualitative) study, conducted in 5 urban sub-districts of Dili, involved in-depth interviews with18 Ministry of Health staff and 6 community leaders, 83 observations of immunization encounters, 37 exit interviews with infants' caregivers at 11 vaccination sites, and 11 focus group discussions with 70 caregivers of vaccination-eligible children ages 6 to 23 months.

Results: The main reasons for low vaccination rates in urban Dili included caregivers' knowledge, attitudes, and perceptions as well as barriers at immunization service sites. Other important factors were access to services and information, particularly in the city periphery, health workers' attitudes and practices, caregivers' fears of side effects, conflicting priorities, large family size, lack of support from husbands and paternal grandmothers, and seasonal migration.

Conclusion: Good access to health facilities or health services does not necessarily translate into uptake of immunization services. The reasons are complex and multifaceted but in general relate to the health services' insufficient understanding of and attention to their clients' needs. Almost all families in Dili would be motivated to have their children immunized if services were convenient, reliable, friendly, and informative.