From the Netherlands the Leiden University Medical Center (LUMC), the Elkerliek hospital and Wageningen University & Research (WUR) are involved in the study.

Global research has revealed that increased pollen in the air is associated with an increase in coronavirus infections. The SARS-CoV-2 virus may exploit the weakened immune response as a result of exposure to pollen. This is not only the case for hay fever patients, but also for people who are not allergic. From the Netherlands the Leiden University Medical Center (LUMC), the Elkerliek hospital and Wageningen University & Research (WUR) are involved in the study. The results were published in the scientific journal PNAS on March 9.

It was already known that exposure to pollen in the spring weakens the immune system’s response to viral respiratory infections, such as the cold virus. This effect occurs in people who are allergic to pollen as well as people who are not allergic. During the outbreak of the coronavirus, it was noted that in many countries the number of infections only began accelerating after the pollen concentration increased. Researchers hypothesised that an immune system that has been weakened due exposure to pollen may be more susceptible to the coronavirus.

Worldwide: increased pollen, increased infections
To examine this, a team of 150 scientists studied the pollen counts from 130 pollen stations in 31 countries, including the Netherlands. The pollen effect was apparent throughout the world at the start of the epidemic. The study shows that the number of infections increased after the pollen concentration rose four days earlier. The infection figures increased by an average of 4 percent after the pollen concentration increased by 100 pollen per cubic metre. The implementation of a lockdown halved this effect, but the amplifying influence of the pollen remained visible.

In the Netherlands as well?
This amplifying effect was also found in the Netherlands, but it declined after strict statistical testing. A variety of strict statistical tests were used to analyse the large amount of information and to determine whether there was a relationship between pollen and the coronavirus. This was a challenging analysis because many different factors determine the rate of infection. Furthermore, the data collection for this study ended after 8 April, which means that a large part of the spring pollen surge was not included in the analysis. This is partly why the connection between pollen and the coronavirus could not be clearly demonstrated for the Netherlands.

Information obtained from: https://www.wur.nl/en/Research-Results/Research-Institutes/Environmental-Research/show-wenr/Increased-pollen-in-the-air-related-to-increase-in-coronavirus-infections.htm