Individual, household structure, and socioeconomic predictors of COVID-19 testing and vaccination outcomes: a whole population linked data analysis.

Introduction: The COVID-19 pandemic produced social inequities in health outcomes between and within nations. Reported inequitable COVID-19 outcomes for ethnic minorities and indigenous peoples are likely to be associated in part because of poorer socioeconomic circumstances experienced by these populations. Understanding these associations within national populations is vital for future pandemic management. Objective: This study explores the social inequity of COVID-19 outcomes within New Zealand over the first 3 years of the pandemic. We aimed to identify policy amenable socioeconomic factors associated with COVID-19 outcomes while adjusting for relevant individual factors and household structure. We also aimed to examine whether ethnic group differences are smaller when accounting for these socioeconomic factors and household structure. Methods: Administrative individual-level data for the New Zealand population was analysed to assess COVID-19 health outcomes during 2020 - 2023. The association between individual (e.g. age, ethnicity, disability status), household structure (e.g. household composition) and socioeconomic (e.g. crowding, housing quality, deprivation) factors and four COVID-19 health outcomes - infection, hospitalisation, mortality, and vaccination status was assessed. Results: Indigenous peoples and ethnic minorities experienced worse outcomes across most COVID-19 outcomes. Adjusting for household structure and socioeconomic factors reduced but did not eliminate these inequities between ethnic groups. Housing issues including high housing mobility, poor quality housing, and household crowding were associated with worse outcomes, as were disability status, no primary health care enrolment, lower household income and older age. The size of these effects also differed for different health outcomes. Conclusions: Ethnic inequity was persistent and likely partly explained by policy-modifiable social factors, despite the relatively minor population health impacts of COVID-19 in New Zealand. We also demonstrate how a range of socioeconomic determinants predict COVID-19 outcomes in different ways.