Evaluating socioeconomic inequalities in influenza vaccine uptake during the COVID-19 pandemic: A cohort study in Greater Manchester, England

• Published in: PLoS medicine 2023-09, Vol.20 (9), p.e1004289
• Main Authors: Watkinson, Ruth Elizabeth, Williams, Richard, Gillibrand, Stephanie, Munford, Luke, Sutton, Matt
• Format: Article
• Language: English
• Subjects: Aged; Analysis; Biology and Life Sciences; Child; Child, Preschool; Children; Cohort Studies; Coronaviruses; COVID-19; COVID-19 - epidemiology; COVID-19 - prevention & control; COVID-19 Vaccines; Demographic aspects; Educational Status; Electronic medical records; Elementary school students; England - epidemiology; Epidemics; Health aspects; Health care; Health care disparities; Health care industry; Humans; Immunization; Influence; Influenza; Influenza vaccines; Influenza Vaccines - therapeutic use; Influenza, Human - epidemiology; Influenza, Human - prevention & control; Medical records; Medical research; Medicine and Health Sciences; Medicine, Experimental; Morbidity; Older people; Pandemics; Pandemics - prevention & control; People and Places; Social aspects; Social Sciences; Socioeconomic factors; State Medicine; Statistics; United Kingdom; Vaccination; Vaccines
• ISSN: 1549-1676; 1549-1277; 1549-1676
• DOI: 10.1371/journal.pmed.1004289

There are known socioeconomic inequalities in annual seasonal influenza (flu) vaccine uptake. The Coronavirus Disease 2019 (COVID-19) pandemic was associated with multiple factors that may have affected flu vaccine uptake, including widespread disruption to healthcare services, changes to flu vaccination eligibility and delivery, and increased public awareness and debate about vaccination due to high-profile COVID-19 vaccination campaigns. However, to the best of our knowledge, no existing studies have investigated the consequences for inequalities in flu vaccine uptake, so we aimed to investigate whether socioeconomic inequalities in flu vaccine uptake have widened since the onset of the COVID-19 pandemic. We used deidentified data from electronic health records for a large city region (Greater Manchester, population 2.8 million), focusing on 3 age groups eligible for National Health Service (NHS) flu vaccination: preschool children (age 2 to 3 years), primary school children (age 4 to 9 years), and older adults (age 65 years plus). The sample population varied between 418,790 (2015/16) and 758,483 (2021/22) across each vaccination season. We estimated age-adjusted neighbourhood-level income deprivation-related inequalities in flu vaccine uptake using Cox proportional hazards models and the slope index of inequality (SII), comparing 7 flu vaccination seasons (2015/16 to 2021/22). Among older adults, the SII (i.e., the gap in uptake between the least and most income-deprived areas) doubled over the 7 seasons from 8.48 (95% CI [7.91,9.04]) percentage points to 16.91 (95% CI [16.46,17.36]) percentage points, with approximately 80% of this increase occurring during the pandemic. Before the pandemic, income-related uptake gaps were wider among children, ranging from 15.59 (95% CI [14.52,16.67]) percentage points to 20.07 (95% CI [18.94,21.20]) percentage points across age groups and vaccination seasons. Among preschool children, the uptake gap increased in 2020/21 to 25.25 (95% CI [24.04,26.45]) percentage points, before decreasing to 20.86 (95% CI [19.65,22.05]) percentage points in 2021/22. Among primary school children, inequalities increased in both pandemic years to reach 30.27 (95% CI [29.58,30.95]) percentage points in 2021/22. Although vaccine uptake increased during the pandemic, disproportionately larger increases in uptake in less deprived areas created wider inequalities in all age groups. The main limitation of our approach is the use of a local d