A recent study suggests that prior infections with common cold viruses, particularly the rhinovirus responsible for colds, may provide some level of defense against COVID-19. Researchers analyzed nasal swabs from over 1,000 participants to explore the relationship between infections with common respiratory viruses and subsequent SARS-CoV-2 infections. The results indicated that individuals who had experienced a cold within the past month had approximately half the risk of developing a COVID-19 infection compared to those who had not. This finding was published in The Journal of Infectious Diseases on August 11.
The study also discovered that when COVID-19 infections did occur, those who had experienced a cold previously tended to have milder cases. Specifically, the viral load—the amount of virus present in an individual’s body—was found to be nearly ten times lower in people who had recently had a cold. This reduced viral load is associated with less severe illness, implying that previous rhinovirus infections may play a protective role in how the body responds to COVID-19.
To better understand why a cold might mitigate the severity of a COVID-19 infection, researchers identified that the smaller viral load was correlated with the production of specific airway defense proteins activated by rhinovirus. These proteins appear to prepare the immune system, facilitating a quicker and more effective response to a coronavirus infection when it occurs. Thus, past infections with rhinovirus might prime the body’s defenses, making it less susceptible to severe outcomes from COVID-19.
Data for the study was drawn from the Human Epidemiology and Response to SARS-CoV-2 (HEROS) study, which had previously established that children tend to experience asymptomatic cases of coronavirus more than adults do. The HEROS study, conducted from May 2020 to February 2021, included nearly 1,400 households in the U.S. where members regularly self-collected nasal swabs for analysis. The current study zoomed in on a smaller sample of these participants to analyze the impact of preceding viral infections.
The researchers noted that certain airway defense proteins were more actively produced in children after experiencing a cold than in adults. Additionally, children in the study were observed to have a higher likelihood of catching colds compared to adults. This could play a significant role in explaining why children tend to have milder COVID-19 illnesses; their immune systems are likely better equipped due to frequent exposure to rhinoviruses.
In conclusion, the favorable effects of past common cold infections on COVID-19 severity present a noteworthy angle in understanding immune responses to different respiratory viruses. This study not only highlights the protective role that rhinovirus infections might play against subsequent COVID-19 infections but also opens doors to further exploration into how respiratory viruses interact with each other and influence health outcomes. Understanding these mechanisms could lead to better prevention strategies and therapeutic options for COVID-19 and other respiratory illnesses.
