A recent common cold may nearly halve risk of COVID-19, study suggests

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Mom with ill son — *Prostock-Studio / iStock*

The common cold may help protect against COVID-19, which may partially explain why children, who are especially vulnerable to most viral respiratory infections, generally have milder SARS-CoV-2 infections than adults, National Jewish Health–led researchers write today in The Journal of Infectious Diseases.

The investigators tested 10,493 repeat nasal swabs from 1,156 US children and adults in the Human Epidemiology and Response to SARS-CoV-2 (HEROS) cohort for 21 respiratory pathogens. They also performed RNA sequencing on 147 swabs from 144 participants taken before COVID-19 infection and 391 swabs from 165 participants before and during rhinovirus infection, which frequently causes the common cold.

"To determine the relationships between prior rhinovirus infection, subsequent SARS-CoV-2 risk, airway antiviral gene expression, and age, we leveraged data from the HEROS cohort, a prospective surveillance study of SARS-CoV-2 in households with children and teens, conducted from May 2020 to February 2021," the researchers wrote.

Rhinovirus also tied to lower SARS-CoV-2 viral load

Participants infected with rhinovirus in the previous 30 days were at a 48% lower risk for COVID-19 (adjusted hazard ratio, 0.52). Among COVID-infected participants, recent rhinovirus infection was tied to a 9.6-fold lower SARS-CoV-2 viral load, or amount of virus in the body, an indicator of infection severity.

Rhinovirus infections, which trigger increased expression of antiviral airway genes, are linked to a lower risk of SARS-CoV-2 infection.

Higher pre-infection expression of 57 genes, including 24 antiviral defense genes, was linked to a lower SARS-CoV-2 viral load, with rhinovirus infection triggering expression of 22 of the antiviral genes. Children expressed higher levels of the antiviral gene signature and were at a 2.2-fold higher risk for rhinovirus infection than adults.

Sensitivity analyses suggested that, compared with more distant and asymptomatic rhinovirus infection, recent and symptomatic infections were associated with greater reductions in COVID-19 risk.

"Rhinovirus infections, which trigger increased expression of antiviral airway genes, are linked to a lower risk of SARS-CoV-2 infection," the study authors wrote. "Frequent rhinovirus infections may enhance this protective gene profile, partially explaining why children experience milder SARS-CoV-2 infections compared to adults."

Study confirms antibiotic exposure as major risk for C diff infection

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Chris Dall, MA

A study in Israel confirms antibiotic use as a major risk factor for Clostridioides difficile infection (CDI) in hospital patients, particularly for those who don't carry the bacterium, researchers reported last week in JAMA Network Open.

For the study, which was conducted from June 2017 through June 2023, researchers analyzed data on patients admitted to a large tertiary medical center in Israel that routinely screens high-risk patients for C difficile carriage. While broad-spectrum antibiotic use is a known risk factor for CDI, the researchers wanted to evaluate the rate of hospital-onset CDI among asymptomatic C difficile carriers compared with noncarriers and assess the role of antibiotic exposure in shaping CDI risk in the two populations.

Antibiotic exposure linked to double the risk of CDI

Among 33,756 hospitalizations (median age, 78 years; 52.8% male), 1,624 (4.8%) had a positive screening result for C difficile. Overall, CDI occurred in 67 (4.1%) of 1,624 carriers and 47 (0.1%) of 32,132 noncarriers.

In the entire cohort, exposure to any antibiotic was associated with double the risk for CDI (hazard ratio [HR], 1.98; 95% confidence interval [CI], 1.24 to 3.16), with each additional day of antibiotic exposure having an HR of 1.08 (95% CI, 1.03 to 1.13). Beta-lactam/beta-lactamase inhibitor combinations were associated with significantly increased risk, with piperacillin-tazobactam showing the most pronounced hazard for CDI (HR, 2.18; 95% CI, 1.41 to 3.36).

Although a positive C difficile screening result at admission was associated with a high risk of CDI (HR, 27.5; 95% CI, 18.7 to 40.3), antibiotic exposure among asymptomatic C difficile carriers was not significantly associated with a further increase in CDI risk (HR, 1.07; 95% CI, 0.73 to 1.58).

The study authors say the findings suggest that, while antibiotic stewardship may reduce CDI risk in noncarriers, additional strategies may be needed for asymptomatic carriers.

"Among carriers, preventive measures in addition to antibiotic stewardship should be evaluated in hospitalized patients and may include probiotics, monoclonal antibodies, or biotherapies," they wrote. "However, further research is necessary to evaluate the potential effectiveness of these interventions, their association with microbiome alterations, and potential changes in antimicrobial resistance patterns among patients and within the hospital environment."