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Improving air quality could reduce severe cases of COVID-19

Exposure to poor air quality worsens COVID-19 patient outcomes, according to a new study from the USC Keck School of Medicine. To understand how air pollution affects those who are vaccinated, the researchers analyzed data from more than 50,000 COVID-19 patients across Southern California. 

The research builds on earlier findings, which helped establish the link between air pollution exposure and COVID-19 severity. The study compared air quality monitoring data with patient medical records, and found that regardless of pollution exposure, vaccines can reduce COVID-19 hospitalizations.

“Fully vaccinated people had almost 90% reduced risk of COVID hospitalization, and even partially vaccinated people had about 50% less risk,” said study co-first author Dr. Zhanghua Chen.

According to the results of the current study, however, pollutants are still harmful even among the vaccinated. For those who were unvaccinated, exposure to fine particles (PM2.5) and nitrogen dioxide (NO2) over the short or long term increased the risk of hospitalization by up to 30 percent. For those who were partially or fully vaccinated, the hospitalization risks were slightly lower, but the difference was not statistically significant.

“These findings are important because they show that, while COVID-19 vaccines are successful at reducing the risk of hospitalization, people who are vaccinated and exposed to polluted air are still at increased risk for worse outcomes than vaccinated people not exposed to air pollution,” said study co-author Dr. Anny Xiang, a senior research scientist at Kaiser Permanente Southern California’s (KPSC) Department of Research & Evaluation.

The researchers analyzed medical records from KPSC patients. Across the health care network, 50,010 patients were diagnosed with COVID-19 in July or August of 2021 when the Delta variant was circulating, and many of these individuals had been vaccinated.

The estimated air pollution exposure was calculated for each participant based on residential addresses. The experts looked at average PM2.5, NO2, and ozone (O3) levels during the one-month and one-year periods before each patient received a COVID-19 diagnosis.

“We investigated both long-term and short-term air pollution exposure, which may influence COVID-19 severity through different mechanisms,” said Chen.

Pollution over the long term is linked to cardiovascular and lung diseases, which are in turn linked to more severe COVID-19 symptoms. In the short term, air pollution exposure may worsen inflammation in the lungs and could alter the immune response to the virus.

The findings suggest that air quality must be improved to reduce severe cases of COVID-19. This spring, the Biden Administration launched the Clean Air in Buildings Challenge to install high-efficiency particulate absorbing (HEPA) filters in schools and other public buildings.

The study is published in the American Journal of Respiratory and Critical Care Medicine

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By Katherine Bucko, Staff Writer

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