People exposed to higher levels of air pollution before the pandemic had lower antibody responses to COVID-19 vaccines, according to a study led by the Barcelona Institute for Global Health (ISGlobal), an institution supported by “la Caixa” Foundation, in collaboration with the Germans Trias i Pujol Research Institute (IGTP). In particular, exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and blank carbon (BC) was associated with about a 10% decrease in IgM and IgG antibody responses in people without prior infection. The findings, published in Environmental Health Perspectives, provide further evidence on the adverse effects of air pollution on the immune system.