Timely vaccination with valid doses in a high coverage country, Oman

Oman has achieved consistently high national immunization coverage; however, the timeliness and validity of vaccine administration remain under-assessed. This study evaluated the timeliness and validity of routine childhood vaccinations to provide a more comprehensive understanding of immunization program performance.

A cross-sectional survey was conducted using WHO cluster sampling, targeting children under five across all 11 governorates and 61 districts in Oman. Data from 17,501 children were collected using the Epicollect5 app and verified through immunization cards and health records. Descriptive statistics, chi-square tests, and WHO operational definitions were used to assess crude coverage, valid doses, timeliness, and dropout rates.

Crude national vaccination coverage was high (94.4-99.9%), with 98.7% of children fully immunized. However, only 78% received valid vaccinations, indicating missed or delayed doses. Timely vaccination rates decreased with age, with notable delays at 18 months. Invalid vaccination rates ranged from 3.3% at birth to 28.1% at 18 months, with significant district-level variation. Dropout rates slightly increased with age, peaking in Muscat and Dhofar.

Oman achieves high vaccination coverage; however, a noteworthy number of children receive invalid doses. This highlights the urgent need to educate parents and healthcare providers on timely administration of valid doses. Assessing mild illnesses and promptly administering vaccinations can improve complete vaccination rates with valid doses.