LOS ANGELES - The spring season correlates with increased pollen counts, and according to a new study, the common allergen could be making COVID-19 infection rates worse.
In the study, published in the journal Proceedings of the National Academy of Sciences of the United States of America, researchers found that higher airborne pollen concentrations were driving increased COVID-19 infection rates.
"Pollen exposure weakens the immunity against certain seasonal respiratory viruses by diminishing the antiviral interferon response," the study’s authors wrote.
The team investigated whether this applied specifically to the COVID-19 virus by performing data analysis from 130 stations across 31 countries. The researchers looked at the areas’ COVID-19 infection, airborne pollen and meteorological factors.
Researchers pulled pollen data from the majority of all pollen monitoring stations worldwide that were operating despite considerable spread of COVID-19 infection rates already by that time.
"We found that airborne pollen, sometimes in synergy with humidity and temperature, explained, on average, 44% of the infection rate variability," the researchers wrote. "Infection rates increased after higher pollen concentrations most frequently during the four previous days."
The study also found an increase in pollen abundance resulted in a 4 percent increase in infection rates, while lockdown measures were not in place. Meanwhile, lockdowns halved infection rates under similar pollen concentrations.
Researchers noted that the COVID-19 pandemic in North America and Europe started during springtime when rising air temperatures were associated with increased social and outdoor activities. This, in return, meant increased environmental exposure to bioaerosols, pollutants or infected humans.
"From all the countries that showed a significant correlation of the infection rate with pollen, this correlation was always positive, which suggests that the mechanism reported for pollen exposure on antiviral immunity to rhinovirus could also be influencing innate immunity toward SARS-CoV-2," the research authors wrote.