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 6 weeks to 4 years, we compare children who became eligible for immunisation during the pandemic to earlier born cohorts. We find for our affected cohorts 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 for the affected cohort was largely achieved for the infancy immunisations, but 4-year coverage remained 6 percentage points below pre-pandemic levels. Uptake initially dropped most among children of European ethnicity and of high-earning parents but catch-up quickly surpassed their Māori, Pacific, and lower-earning 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.