Throughout the COVID-19 pandemic, experts from the Dana and David Dornsife School of Public Health have researched disparities in testing, vaccination, health care access and other markers of the pandemic response.

A September 2022 study in the American Journal of Epidemiology examined the period from December 2020 through September 2021, when the U.S. first started distributing the vaccines, and looked at full vaccination rates in neighborhoods of 16 large U.S. cities, including Philadelphia, Austin, San Francisco, Chicago and New York City.

Researchers at Drexel’s Urban Health Collaborative applied the Centers for Disease Control’s Social Vulnerability Index — a measure that includes socioeconomic, housing, minority status, language and other factors to assess a community’s resilience against human suffering and financial loss when faced with a crisis — and found that neighborhoods with higher levels of social vulnerability had the lowest vaccination rates.

Specifically, COVID-19 vaccination coverage was 0.75 times, or 16 percentage points, lower in neighborhoods with the highest social vulnerability, as compared with those with the lowest.

This was expected, the authors acknowledged, however they discovered that cities in the West generally displayed narrower inequities in both the absolute and relative scales.

“This pattern mirrors what we have described before with COVID-19 itself,” says lead author Usama Bilal, an assistant professor of epidemiology in the Department of Epidemiology and Biostatistics. “What was surprising is the degree of variability. We found that some cities in California, along with our own city of Philadelphia, had a narrower gap between neighborhoods. We did not study factors driving these narrower inequalities, but we know that California has an extensive COVID-19 equity plan and that some of its cities made an effort to vaccinate people in the more vulnerable neighborhoods.”

He hypothesized that Philadelphia performed well because the city prioritized vaccination drives in certain ZIP codes early on. Community groups, such as the Black Doctors COVID-19 Consortium organized drives to vaccinate Black and Latino citizens.

“We cannot know for sure with our data whether these efforts were the reason for Philadelphia’s narrower gap in vaccination, but they are definitely very important initiatives,” Bilal says.