Table 2 Association between influenza vaccination and SES, by two-measure SES

 LaVela 2012 [25]; US

Education and employment (Individual)

Education level: did not graduate HS, HS or more

Employment status: currently employed for wages, or not

Sociodemographic characteristics, characteristics of multiple sclerosis, comorbidities

Behavioral Risk Factor Surveillance System and Multiple Sclerosis Health Care Questionnaire; National survey (2003)

No association. There was no significant association between influenza vaccination, being in paid employment, or having completed high school among men age 50 or older with multiple sclerosis.

 Lu 2015 [26]; US

Education and employment (Individual)

Employment status (employed, unemployed, not in work force)

Education level (less than HS, HS, college or more)

Sociodemographic variables and health service variables

National Health Information Survey; National survey (2012)

Positive association. Adults aged 19–64 with college education or higher were more likely (1.18, 1.09–1.27CI) to receive a vaccination compared to persons with HS, as were persons aged 65 and older (1.11APR, 1.04–1.18CI).

Unemployed adults were less likely to be vaccinated compared to employed adults (0.89APR, 0.80–1.00CI), but among the elderly, unemployed persons were more likely to be vaccinated (1.10APR, 1.03–1.17CI).

 Barbadoro 2016 [27]; Italy

Education and income (Individual)

Education level (low, medium-low, medium-high, high)

Wealth (1 = low, 2, 3, 4 = high)

Sociodemographic and clinical variables

Health and Health Care use in Italy; National survey (2004–05; 2013)

Mixed findings. Obese persons with medium-high levels of education were less likely to be vaccinated compared to persons with low levels of education in two age groups: 18–64 years (0.77OR, 0.62–0.96CI) and 64 and older (0.79OR, 0.63–0.98CI).

No association was found with income.

 Blackwell 2015 [28]; US

Education and income (Individual and household)

Highest level of parental education in household (less than HS, HS diploma, GED, some college, college degree)

Poverty ratios for 2010: below federal threshold (less than 1.0, 1 to < 2 times threshold, 2 to < 4 times threshold, 4 times or more threshold)

Sociodemographic and health status

National Health Interview Survey; National survey (2009–10)

Positive association. Children of parents whose highest level of education was HS or GED (0.82ARR, 0.68–1.0CI) or less than a HS diploma (0.72ARR, 0.57–0.92) were less likely to be vaccinated compared to those with parents who had some post-secondary education.

Children living 4 times or more above the poverty threshold were more likely to be vaccinated compared to those living less than 1 times below (0.75ARR, 0.59–0.96CI), 1 to < 2 times below (0.69ARR, 0.57–0.84CI), 2 to < 4 times below (0.77ARR, 0.66–0.90CI).

There was no association between education and income and receipt of a second pH1N1 vaccination.

 CDC 2013 [29]; US

Education and income (Individual and household)

Level of education (less than 12 years, 12 years, more than 12 years)

Federal poverty level for 2010 (at or below the poverty level, above the poverty level)

None reported

Massachusetts Pregnancy Risk Assessment Monitoring System; State survey (2009–10)

Positive association. Pregnant women with less than 12 years (56.6%, 45.0–67.5CI) of education had lower seasonal vaccination rates compared to those with 12 years (63.1%, 54.4–71.1CI) or greater than 12 years education (71.1%, 66.0–75.5CI). No association was found with pH1N1 vaccine.

Pregnant women living above the federal poverty line had greater coverage of seasonal influenza vaccination (70.5%, 65.6–75.0CI) compared to those living at or below it (56.1%, 47.5–64.3%), but no association was found for pH1N1.

 Dlugacz 2012 [30]; US

Education and income (Individual)

Education level (less than HS, HS, college graduate, graduate degree)

Income level ($75,000 or more, $50,000–$75,000, less than $50,000)

Sociodemographic variables

Survey of postpartum women on labour and delivery service; Survey administered in 4 hospitals in Nassau County New York, and Queens County in New York City (2010)

Positive association. In the unadjusted model, each increase in level of education among postpartum women resulted in higher levels of vaccination. For income levels, the highest income group was twice as likely to have been vaccinated than the middle and low-income group. The adjusted ORs were not reported for income and education separately.

When looking at the combined effects of income and education, higher levels resulted in 43–69% of pregnant women receiving a vaccine when recommended by a healthcare provider, compared to 4–10% when not recommended.

 Gorska-Ciebiada 2015 [31]; Poland

Education and income (Individual)

High (above 2000 pln) or low income (2000 pln or lower)

Education level (primary, secondary, technical, university)

Sociodemographic, health status, and clinical variables

Survey of elders in an internal medicine and diabetology outpatient clinic in Lodz; Survey of clinic outpatients (2012–13)

Mixed findings. Elderly outpatients with diabetes aged 65 and older were more likely to be vaccinated if they had higher income (5.34OR, 2.38–12.16CI).

 Hellfritzsch 2017 [32]; Denmark

Education and income (Individual and household)

Education level, in years beyond primary school (none, less than 3 years, 3–4 years, more than 4 years, other)

Annual household income in Danish Kroner (less than $99,000, $100,000–$149,000, $150,000–$249,000, $250,000–$374,999, $375,000–$524,000, more than $524,000)

Age and sex

Questionnaire from Centre for Public Health; National survey (2006)

Mixed findings. There was no association between seasonal influenza vaccination and education level among Danes ages 65–79.

For income, only the middle-income group (1.10PR, 1.00–1.21CI) was associated with seasonal influenza vaccination after controlling for age and sex.

 Hoeck 2013 [33]; Belgium

Education and income (Household)

Highest level of education (no degree or primary education, lower secondary, higher secondary, higher education)

Household income (<€750, €750–€1000, €1000–€1500, €1500–€2500, and > €2500)

Sociodemographic variables, health status, and risk factors

Belgian Health Interview Survey; National survey (2004; 2008)

No association. There was no significant association between level of education or household income with influenza vaccination.

 Kwon 2016 [34]; South Korea

Education and income (Individual and household)

Education level: low (less than 6 years) or high (more than elementary school)

Household income (less than $1000 USD per month, or $1000 USD or more per month)

Sociodemographic variables, health status, and behavioural risk factor variables

Korean National Health and Nutrition Examination Survey; National survey (2007–09)

Mixed findings. Higher education was associated with higher levels of vaccination (1.27OR, 1.03–1.57CI) among the elderly 65 and older. No association with income was found.

 Lee 2015 [35]; South Korea

Education and income (Individual and household)

Education level: low (elementary), middle (middle or high school), high (college or higher)

Household income (low [Q1), middle [Q2, Q3], high [Q4])

Sociodemographic factors and health status variables

Korea National Health and Nutrition Examination Survey; National survey (2010–11)

Mixed findings. No significant relationship was found between influenza vaccination and education for any age group.

Younger adults aged 19–50 years were less likely to be vaccinated if they were in the highest income group (0.33OR, 0.26–0.40CI), compared to the lowest. For adults age 50 or older, no significant association was found.

 Lee 2012 [36]; US

Education and income (Individual)

Education level (none, 5 years or less, more than 5 years)

Income ($50,000 or less, more than $50,000)

Sociodemographic variables, health status variables, education in the US and acculturation level

Survey of Korean-Americans; Nationally representative survey (2005–07)

No association. No significant associations were found between education or income and influenza vaccination among adult Korean women living in California.

 Lu 2012 [37]; US

Education and income (Individual)

Education level (less than HS, HS graduate, college)

Income (below $20,000, $20,000-50,000, $50,000 or higher)

Sociodemographic factors, health status variables, and insurance status

Behavioral Risk Factor Surveillance System; National survey (2009–10)

Positive association. Among healthcare personnel, adults were more likely to be vaccinated against H1N1 or seasonal influenza if they had incomes above $50,000. For non-healthcare personnel, only seasonal influenza vaccination was associated with higher income levels.

For education, significant and positive associations were found for H1N1 and seasonal influenza vaccinations, whereby the highest education group had the highest proportion of vaccine.

 Lu 2016 [38]; US

Education and poverty (Individual)

Education level (HS or less, some college or college graduate, above college graduate)

Poverty level (at or above poverty, below poverty)

Sociodemographic variables and health status variables

National Health Information Survey; National survey (2013; 2014)

Mixed findings. Healthcare personnel with college education were significantly more likely to have received influenza vaccination compared to those with high school or less (1.27 PR, 1.11–1.46 CI). There was no relationship found with poverty and vaccination status for healthcare personnel.

For non-healthcare personnel, any level of education higher than high school was significantly associated with vaccination. (College level compared to high school or less was 1.10 PR, 1.06–1,15 CI; above college 1.34 PR, 1.26–1.42 CI).

Non-healthcare personnel were more likely to be vaccinated if they were at or above the poverty level (1.08 PR, 1.02–1.14 CI) compared to those below it.

 Schuller 2013 [39]; US

Education and poverty (Individual)

Mother’s education level (college graduate less than 12 years, 12 years, more than 12 years, non-college graduate)

Poverty status (above poverty level with $75,000 or more, or below poverty level)

Sociodemographic variables

National Immunization Survey; National survey (2008–09)

Positive association. Mothers who graduated from college were more likely to vaccinate their children compared to mothers with a high school degree (0.57OR, 0.51 to 0.63 CI).

Mothers who lived above the poverty level with incomes of $75,000 or more were significantly more likely to vaccinate their children compared to those who lived above the poverty level with lower levels of income (0.64 OR, 0.58 to 0.71 CI) or below it (0.63 OR, 0.56 to 0.71 CI).

 Takayama 2012 [40]; US

Education and income (Individual)

Education (less than HS, more than HS)

Annual income (less than $35,000, more than $35,000)

Sociodemographic variables, health behavior variables, and physical health status

Behavioral Risk Factor Surveillance System; National survey (2009)

Positive association. Among elderly adults 60 years and older, having less than a high school education was significantly associated with lower levels of vaccination (0.95 OR, 0.92 to 0.99 CI).

For older adults and adults aged 16 to 64 years, lower income was significantly associated with lower levels of vaccination.

 Zhai 2017 [41]; US

Education and poverty (Individual)

Mothers education level (less than 12 years school, 12 years of school, more than 12 years of school, not a college graduate)

Poverty status (above poverty level with more than $75,000 per year, above the poverty level with less than $75,000 per year, at or below the poverty level)

Not reported

National Immunization Survey Flu (NIS-Flu); National survey of households with children aged 6 months to 17 years (2015)

Positive association. In 2012–2013, higher levels of mother’s education were significantly related to vaccination among children aged 6 months to 8 years, increasingly, for every level of education. In the 2013–2014 season, only having a college degree was significantly related to vaccination, while having 12 years of school was significantly less likely to be vaccinated.

Poverty status was significantly related to higher levels of vaccination for children whose parents lived above the poverty line and made more than $75,000 per year, compared to those living with lower incomes in both seasons.

 Muscoplat 2013 [42]; US

Income and poverty (Neighbourhood)

Percentage of residents in a ZIP code with incomes below the federal poverty level (<$35,000; $35,000 to <$40,000; $40,000 to $50,000; >$50,000)

Percentage of residents with incomes below the poverty level (< 3.0%; 3.0 to < 5.0%; 5.0 to 8.0%; > 8.0%)

Poverty and minority status

Minnesota Immunization Information Connection; Immunization database (2009–10)

Mixed findings. There were significant differences in H1N1 vaccination rates when comparing percentage of residents living below the poverty line. The results show that generally, areas where there were greater proportions of persons living below the poverty line (5 to 8%, or 8% and higher) had higher vaccination rates than in areas where there were lower proportions (3 to < 5%, less than 3%).

Median family income was significantly related to vaccination rates. In areas with higher vaccination rates (20% and above), higher income was associated with higher vaccination levels. In areas where vaccine rates were less than 20%, lower income levels were associated with higher levels of vaccination.