Vaccination Coverage Among Children Aged 19 – 35 Months and 6 Years, American Samoa, 2008-2009

Background: American Samoa conducted their first island-wide household vaccination coverage survey in 2008-2009, following a 2007-08 mumps outbreak.

Objectives: To measure the vaccination coverage among young children in American Samoa and assess the utility of different sources of vaccination data

Methods: On the main island, every fourth house found in each village was screened for children aged 1, 2, or 6 years in October/November 2008. In Manu’a District islands, all households were screened in November 2008 or June 2009. Interviewers collected demographic and shotcard information, and consent for medical record abstraction. Household-retained shotcard data obtained during household interviews, medical chart abstraction data, and a combination of dates from both sources were used to calculate weighted coverage estimates of individual vaccines (DTaP, Polio, MMR, HiB, and HepB) and for the 4:3:1:3:3 and 5:4:2:3:3 vaccine series.

Results: Among the 647 children 1, 2, or 6 years in 2,241 households, 304 were 19-35 months-old and 196 were 6 years-old. Among 19-35 month-olds, coverage with the 4:3:1:3:3 vaccine series was 53% based on shotcard and 64% based on medical chart. When both sources were combined coverage increased to 75% with doses of vaccine recorded in the shot card but not in the medical chart. The same discrepancy appeared among 6 year-olds, where coverage with the 5:4:2:3:3 series was 28% based on shotcard, 57% based on the medical chart, and 67% using both sources. Vaccination coverage was generally >80% for individual vaccines.    

Conclusions: Neither shotcard- nor medical chart-based coverage estimates are complete. Incomplete documentation could lead to administration of early, invalid doses of vaccine in under-vaccinated children or excess doses in fully-vaccinated children. Improved documentation of dates of vaccination, both historical and administered on-island, in the medical chart would permit more accurate estimates of coverage based on program data and would conserve limited vaccine and staffing resources.