Every winter coughs and sneezes run rampant through the population, but some people find themselves sick with the common cold time and again whereas others do not. Although immune memory generated from previous infections can partially explain why some people might be protected, it is not sufficient to explain the whole story.

Researchers at Imperial College London trying to better understand what makes us susceptible to the common cold, looked at the state of the airways in healthy volunteers before exposing them to Respiratory Syncytial Virus (RSV). RSV is one of a number of viruses which can cause common cold symptoms in healthy adults, but it can prove fatal in infants and the elderly.

In a paper published in Science, these researchers showed that people with bacteria-fighting cells, called neutrophils, in their airways before viral exposure were more likely to become infected with RSV. In this case, by being primed to tackle bacterial infections, their immune systems were less prepared to fight off a virus.

This finding could be used to identify people who might be more likely to become infected with RSV as well as further our understanding of how viruses affect us. These findings may prove relevant for other viruses such as influenza and coronaviruses.

Such a discovery would not have been possible without a challenge study in which study volunteers are safely exposed to the virus. This allows researchers to capture information before, during and after viral exposure, something which researchers at Imperial College London now hope to do with Sars-CoV-2, the virus responsible for the COVID-19 pandemic.