According to a study published in the journal Environmental Health Perspectives, air pollutants can affect the bodys immune responses. The study showed that people exposed to higher levels of air pollution before the pandemic were more likely to have lower antibody responses to COVID-19 vaccines.

However, the researchers stated that the role of long-term exposure to air pollution on hybrid immunity needs further investigation. Dr. Carlota Dobano, a researcher from ISGlobal, stated that air pollution can induce chronic inflammation, which has been associated with a negative effect on vaccine efficacy.

In the study, the researchers analysed the data collected from 927 participants. The participants were asked to answer questionnaires. Their blood samples were also taken in the summer of 2020 and in 2021. The researchers used blood samples to measure IgM, IgG, and IgA antibodies to five viral antigens.

The findings of the study showed that in uninfected individuals, pre-pandemic exposure to PM2.5, NO₂, and BC was associated with a 5–10% reduction in vaccine-induced spike antibodies. Both early IgM responses and late responses measured by IgG demonstrated a decrease in antibodies. Lower IgG levels remained for several months following immunisation, and the IgG response to the initial dose peaked later in those exposed to greater levels of air pollution. 

(Source:https://www.business-standard.com/health/air-pollution-can-affect-your-covid-19-vaccine-efficacy-says-study-123040600381_1.html#:~:text=%22Air%20pollution%20can%20induce%20chronic,in%20children%2C%22%20she%20added.)