This case study illustrates how studies using secondary quantitative survey data can frame research questions to illuminate both patterns of inequalities within and across social categories and some of the potential structural drivers of these.

In this USA-based study, Liu and Li set out to understand why some people are not taking up the COVID-19 vaccine in order to contribute to development of approaches to improving vaccine coverage. Their specific research questions were:

1) How does COVID-19 vaccine hesitancy, measured in different dimensions of determinants, vary across sociodemographic groups?
2) How does COVID-19 vaccine hesitancy change at different rates across sociodemographic groups?
3) How are disparities in COVID-19 vaccine hesitancy across sociodemographic groups associated with the state-level political environment?
4) How do different sociodemographic characteristics such as race, gender, and class intersect to affect COVID-19 vaccine hesitancy?

The equity lens provided by these questions has three dimensions: (i) the potential for different experiences and outcomes across “sociodemongraphic groups”; (ii) possible intersections between these groups e.g. between gender, race and class; and (iii) the potential impact of state-level political environments on vaccine uptake.

Their study design involved secondary data analyses. They used publicly available longitudinal microdata from the national Household Pulse Survey (HPS) conducted weekly since April 2020. It includes questions on employment status, food security, housing, physical and mental health, access to unemployment insurance and health care, education disruptions, and attitudes to COVID vaccine.

They used multi-level mixed-effect logistic regression models with statel level intercepts effects to predict each of the vaccine hesitancy measures highlighted in their four research questions: changes over time across gender, race and class; rates of change over time in these groups; changes in vaccine hesitancy in these groups across States; and intersections between these groups.

Their key findings paint a lot more complecated picture of vaccine hesitance.

1) The partisan divide embedded in the COVID-19 vaccine hesitancy:

It is concerning but only tells one side of the story. On the other hand, the variations across the three dimensions of vaccine hesitancy and the sociodemographic stratification patterns indicate that hesitancy towards COVID-19 vaccines is not simply a partisan issue shaped by misinformation and conspiracy theories. Instead, it involves complex concerns related to confidence and circumspection issues that may have their roots in structural inequality but could change across time as the situation evolves.

2) Significant racial differences in hesitancy towards COVID-19 vaccines & and temporal and spatial changes across racial groups:

Blacks are significantly more likely to develop vaccine hesitancy than other racial/ethnic groups during early periods of vaccine release – however, this is largely driven by confidence and circumspection issues but not so much by complacency issues. This means Blacks are hesitant not because they underestimate the risks of COVID-19, but because they have concerns with the effectiveness and side effects of COVID-19 vaccines and incline to calculate the costs and benefits carefully before making a vaccination decision. Moreover, vaccine hesitancy among Blacks declines dramatically across time, faster than any other racial groups. In fact, in the most recent data collection period (March 17–29, 2021), the predicted probability of vaccine hesitancy among Blacks has decreased to the same level as that of Whites – including overall hesitancy and hesitancy due to confidence and circumspection.

3) Important gender differences:

They observed a higher level of overall vaccine hesitancy among women than men in early periods. However, when examining different dimensions of vaccine hesitancy, women are more likely to develop hesitancy due to circumspection, and this kind of hesitancy declines faster than hesitancy due to confidence and complacency.

4) An important intersection between race and gender:

They observed the highest level of hesitancy among the most marginalised group i.e. Black women. These findings are consistent with previous literature linking vaccine hesitancy to historical and current systemic racism and discrimination.

5) The interaction effects of state partisanship with individual-level variates, particularly race:

They observed a promising drop of vaccine hesitancy over time among the Black community, it is worth noting that unlike other racial/ethnic groups, Blacks living in Democratic states did not demonstrate a much lower level of vaccine hesitancy than their counterparts who live in Republican states.

They did not craft recommendations for action per se but these findings allude to a number of important points for future strategies to reduce sociodemographic disparities in vaccination. For instance, they observe a larger racial disparity in vaccine hesitancy in states that are more Democratic, where other racial groups tend to have low levels of vaccine hesitancy. These findings call for more targeted policies and strategies to improve vaccination rates according to local and community contexts.