Adherence to public health recommendations, restrictions and requirements among priority populations at risk for COVID-19 mortality and infection in Victoria, Australia: a serial cross-sectional study.

INTRODUCTION: To examine adherence to COVID-19 public health measures among culturally and linguistically diverse (CALD) and low socioeconomic status (SES) populations in the Australian state of Victoria using a unique longitudinal cohort. METHODS: The Optimise Study was a mixed-methods longitudinal cohort and social networks study (September 2020-December 2023) assessing the impact of COVID-19 and related public health measures in Victoria, Australia. We used a serial cross-sectional design to analyse adherence to public health recommendations, restrictions and requirements. The study examines two 28-day periods during the COVID-19 pandemic in Victoria: 23 April-20 May 2021 ('non-lockdown') and 13 September-10 October 2021 ('lockdown'). We explored adherence to three categories of COVID-19 public health measures-Recommendations (non-enforced, longer-term), Restrictions (mandated during lockdown periods) and Requirements (mandated, longer-term)-among participants who completed questionnaires during these periods. Participants were grouped as (1) non-CALD high SES (did not meet CALD or low-SES criteria), (2) CALD or (3) non-CALD low-SES. Primary outcomes were adherence to recommendations, restrictions and requirements during the two study periods. RESULTS: Of 782 participants recruited, 579 (75%) completed a survey or diary during at least one study period and were included in the analysis. Of these, 275 (47%) were in the 'non-CALD high-SES' group, 114 (20%) in the CALD group and 190 (33%) in the 'non-CALD low-SES' group. Across all groups, risk-reduction behaviours increased during the lockdown. CALD participants showed higher adherence to some recommendations and restrictions compared with the other groups. Overall, 28% left home while awaiting a COVID-19 test result, commonly due to work. CONCLUSIONS: High adherence among CALD and 'non-CALD low-SES' groups suggest structural barriers, rather than behavioural non-compliance, contributed to higher COVID-19 impacts, highlighting the need for tailored support. During future public health emergencies, better supports are needed for individuals working outside of home to remain in isolation while awaiting a test result.