Assessing the impact of the COVID-19 pandemic on childhood vaccine uptake with administrative data.

This study examines the impact of the COVID-19 pandemic on childhood vaccination coverage in New Zealand using population-wide administrative data. For each immunisation event from ages 6 weeks to 4 years, we compare vaccine uptake of children who became eligible for immunisation during the pandemic to earlier-born cohorts whose immunisations were due before the pandemic. We find that the initial phase of the pandemic had, on average, small or nil effects on timely immunisation at the four infancy events, but a large effect at the 4-year event of -15 percentage points. Nine months after eligibility, catch-up among the pandemic-affected cohorts was largely achieved for the infancy immunisations, but 4-year coverage remained 6 percentage points below pre-pandemic levels. Vaccine uptake at 4 years initially dropped most among children of European ethnicity and of non-beneficiary parents but catch-up quickly surpassed their Māori, Pacific, and beneficiary counterparts for whom sizeable gaps in coverage below pre-pandemic levels remained at the end of our observation period. The pandemic thus widened pre-existing inequalities in immunisation coverage.