Socioeconomic Inequalities in SARS-CoV-2 Infection and COVID-19 Health Outcomes in Urban Italy During the COVID-19 Vaccine Rollout, January-November 2021

Abstract

This study analysed the evolution of the association of socioeconomic deprivation (SED) with SARS-CoV-2 infection and COVID-19 outcomes in urban Italy during the vaccine rollout in 2021. We conducted a retrospective cohort analysis between January and November 2021, comprising of 16,044,530 individuals aged ≥ 20 years, by linking national COVID-19 surveillance system data to the Italian SED index calculated at census block level. We estimated incidence rate ratios (IRRs) of infection and severe COVID-19 outcomes by SED tercile relative to the least deprived tercile, over three periods defined as low (0-10%); intermediate (> 10-60%) and high (> 60-74%) vaccination coverage. We found patterns of increasing relative socioeconomic inequalities in infection, hospitalisation and death as COVID-19 vaccination coverage increased. Between the low and high coverage periods, IRRs for the most deprived areas increased from 1.09 (95%CI 1.03-1.15) to 1.28 (95%CI 1.21-1.37) for infection; 1.48 (95%CI 1.36-1.61) to 2.02 (95%CI 1.82-2.25) for hospitalisation and 1.57 (95%CI 1.36-1.80) to 1.89 (95%CI 1.53-2.34) for death. Deprived populations in urban Italy should be considered as vulnerable groups in future pandemic preparedness plans to respond to COVID-19 in particular during mass vaccination roll out phases with gradual lifting of social distancing measures.

Keywords: COVID-19 vaccination; Health inequalities; Socioeconomic deprivation.

Fig. 1

Flowchart showing the inclusion and exclusion criteria for the study population. SED, socioeconomic deprivation. ^Non-urban: intermediate and thinly populated areas (EUROSTAT¹⁵). *When the 2011 census population estimates by census block, age and sex < population with SARS-CoV-2 infection, the latter values were considered as the respective census block population sizes

Fig. 2

Age adjusted weekly incidence rates of SARS-CoV-2 infection (A), COVID-19 hospitalisation (B) and COVID-19 death (C), per 1,000,000 person-days, by census block socioeconomic deprivation terciles; urban Italy, January-November 2021. Background colours correspond to the three consecutive periods defined as low (0 to 10%), intermediate (> 10 to 60%) and high (> 60 to 74%) vaccination coverage, with at least one COVID-19 vaccine dose. D1 (in red), D2 (in green) and D3 (in blue) correspond to the least, moderately and most deprived census block areas respectively. Age standardisation was conducted using the revised European Standard Population (EUROSTAT) [14]

Fig. 3

Fully adjusted incidence rate ratios (IRR) of SARS-CoV-2 infection (A), COVID-19 hospitalisation (B) and COVID-19 death (C), by census block socioeconomic deprivation (SED) terciles in urban Italy, and vaccination coverage period. Low vaccination coverage (0 to 10%) / January 1–March 24, 2021; intermediate coverage (> 10 to 60%)/March 25–July 25, 2021; high coverage (> 60 to 74%)/July 26–November 4, 2021, with at least one vaccine dose. The referent tercile (i.e. vertical line at IRR = 1) represents the least deprived areas (i.e. D1 areas). D2 (in green) and D3 (in blue) correspond to the moderately and most deprived census block areas respectively. The models are adjusted for sex, NUTS1 level areas and the interaction between vaccination coverage period and age; with an interaction effect for vaccination coverage period on SED