A recent bout of the common cold may be a defense against a COVID-19 infection.
A study that included the nasal swabs of more than 1,000 participants assessed whether infections with common respiratory viruses — including rhinovirus, the perpetrator of a cold — impacted later coronavirus infections. Having had a cold in the past month was linked to about half the risk of developing a SARS-CoV-2 infection compared with those who’d had a cold-free month, researchers report in The Journal of Infectious Diseases on August 11.
When a coronavirus infection did occur, having a cold beforehand made COVID-19 milder — there was less coronavirus for the body to contend with, the researchers found. The viral load, a measure of the amount of virus in a person’s body, was almost 10 times lower when a person had a cold prior to COVID. A smaller viral load is associated with less severe illness.
The researchers also looked at why a cold might prevent or temper COVID-19. The smaller viral load was linked to the production of certain airway defense proteins activated by rhinovirus. It appears that having a cold means those proteins are ready if the coronavirus appears.
The new work analyzed data from the Human Epidemiology and Response to SARS-CoV-2 (HEROS) study, which had previously found that kids are more likely than adults to have asymptomatic coronavirus infections. HEROS, conducted from May 2020 to February 2021, included almost 1,400 U.S. households, whose members regularly self-collected nasal swabs.
In the new study, which explores kids’ tendency towards milder coronavirus infections, the team focused on a smaller subset of participants. The study compared coronavirus positive and negative cases from the 30 days before a household’s first infection, genetically analyzed nasal swabs from rhinovirus infections and tracked how often people got colds. Some of the airway defense proteins were more highly activated in kids after a cold than in adults, the researchers report. And compared to adults, kids in the study were more likely to get colds.
