Abstract
Background: The suboptimal compliance to vaccinations continues to be a major public health problem worldwide.
Objectives: To estimate the proportion of children who have delayed vaccinations and to investigate the factors associated with such delays.
Methods: This cross-sectional study was conducted at the Maternity and Children Hospital in Al- Madinah Al-Munawarah, Kingdom of Saudi Arabia, from January to March 2018. The participants, including 149 mothers with children younger than 24 months, were recruited from this hospital. Face-to-face interviews were conducted using a 15-item questionnaire that asked about socio- demographic characteristics, the vaccination statuses of their children, and the causes of delayed vaccinations if available.
Results: Only 40.9% of the children had received vaccinations either on time or with delays of a few days, while vaccinations for 59.1% of the children had been delayed for longer periods of four weeks or more. The most common risk factors for delayed vaccinations were illness of the child at the vaccination time (42.2%), unavailability of the vaccine (22.9%), negligence (17.4%), and other delays based on a physician's advice (16.4%).
Conclusions: A large proportion of children have poor compliance to vaccination appointments, and vaccination providers should be alert to all opportunities to improve the immunization coverage and the need to provide accurate knowledge about the real contraindications to vaccination.

Key words: child vaccination; delayed vaccination; delayed immunization; immunization coverage; vaccination Prevalence.