COVID-19 by Income and Vaccination in 81 Los Angeles Communities, 2020–2021

COVID-19 has hit socially vulnerable communities hardest — those with lower incomes, less education and larger shares of minority residents. Researchers from Cedars-Sinai Medical Center, City of Hope and the Los Angeles County Department of Health Services looked at how the gap by income changed once vaccines arrived, across 81 communities in Los Angeles with 5,083,093 residents.

The approach

Community-level case and vaccination data, from the Los Angeles Times repository of California Department of Public Health figures, were linked to Census data. A statistical model estimated COVID-19 incidence and vaccination coverage across communities ranked by median household income, adjusting for age, sex, place of birth, race and ethnicity, education, health insurance and household size. The researchers compared the peak months of three surges:

• July 2020 and January 2021, before vaccines were available; and
• September 2021, after vaccines became widely available in April 2021.

COVID-19 incidence by community income percentile, Los Angeles, 2020–2021. Image from CDC’s page.

Before vaccines

The poorest communities were hit far harder. Compared with the highest-income tenth of communities, incidence in the lowest-income tenth was:

• 6.6 times higher in July 2020; and
• 4.3 times higher in January 2021.

After vaccines

By September 2021 the gap had disappeared: incidence did not differ significantly between the richest and poorest communities.

That happened even though vaccination coverage still followed income — 59.4% in the lowest-income communities against 71.5% in the highest. Vaccination lowered incidence in every income group, but its effect was largest in the poorest communities: a 20% rise in community vaccination was estimated to cut incidence by an extra 8.1% there compared with the richest communities.

Why vaccination mattered most where incomes were lowest

People in lower-income communities may face more exposure — denser housing, more use of public transportation, and service jobs that cannot be done from home — so protecting them prevents more infections. Higher earlier infection rates may also have left more people with some immunity: before the third surge, 17% of people in the lowest-income communities had tested positive, against 4% in the highest.

California tried to narrow the vaccination gap, for example by setting aside 40% of vaccination appointments in March 2021 for communities in the lowest quarter of the California Healthy Places Index, which combines 25 measures of income, education, health care access, housing, environment, transportation and social conditions. Every community in the lowest income tenth in this study fell in that lowest quarter. Such efforts probably helped keep coverage within a fairly narrow range, 59.4%–71.5%, across income groups.

Limitations

• The data were for communities, not individuals, so the effect of each person’s vaccination and prior infection could not be measured directly.
• Differences in access to and use of testing between communities could not be adjusted for.
• Results may not apply outside Los Angeles, or to other waves and variants.

What it means

Before vaccines, the pandemic fell hardest on the poorest communities; vaccination helped close that gap. The authors call for plans to protect lower-income communities quickly during future pandemics while vaccines are developed, and for continued work to improve access to vaccination and vaccine confidence in the communities hit hardest.

Sources

Based on Masterson JM, Luu M, Dallas KB, Daskivich LP, Spiegel B, Daskivich TJ, "Disparities in COVID-19 Disease Incidence by Income and Vaccination Coverage — 81 Communities, Los Angeles, California, July 2020–September 2021," Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; rewritten in hubnx’s own words.