Common respiratory infections may have protected children from COVID-19, study suggests

Common respiratory infections may have protected children from COVID-19, study suggests

The new study suggests that, by repeatedly activating antiviral and proinflammatory innate immune responses, common respiratory viruses and bacterial infections may have helped protect children from SARS-CoV-2. Credit: 2024 Watkins et al. Originally published Journal of Experimental Medicine. 10.1084/gem.20230911

Analyzing nasal swabs taken during the pandemic, researchers at Yale School of Medicine suggested that the persistent presence of other viruses and bacteria may have helped protect children from the worst effects of COVID-19 by boosting their immune systems. Their results are published July 1 Journal of Experimental Medicine ,JE Meter,

Children are generally more susceptible to respiratory infections such as the common cold than adults, and yet, for unknown reasons, the SARS-CoV-2 virus causes less severe symptoms in children than in adults, resulting in lower rates of hospitalization and death during the COVID-19 pandemic.

The innate immune system provides the first line of defence against viruses and bacteria, producing a range of anti-viral and proinflammatory proteins to prevent infection while the body develops other, more targeted, immune responses such as antibodies. Studies have shown that compared with adults, the innate immune system is more active in the nasal passages of children and may therefore be better at preventing the early stages of SARS-CoV-2 infection. But the reason for this increased activity is unknown.

“Previous studies have suggested that increased nasal innate immunity in children occurs as they age due to underlying intrinsic biological mechanisms,” says Ellen F. Foxman, MD, associate professor of laboratory medicine and immunobiology at Yale School of Medicine and senior author of the study. JE Meter “But we thought it might also be due to the higher burden of respiratory viruses and bacterial infections in children,” the study says.

To investigate whether frequent respiratory infections are responsible for enhanced nasal innate immunity in children, Foxman and colleagues reanalyzed more than 600 nasal swabs originally taken during the pandemic from pediatric patients undergoing elective surgery or emergency room evaluation.

After initially testing only for the presence of SARS-CoV-2, Foxman and his colleagues rescreened the samples for 19 different respiratory viruses and bacteria, as well as measuring levels of antiviral and inflammatory proteins produced by the innate immune system.

The researchers found that many children – even those with no symptoms – were infected with respiratory pathogens other than SARS-CoV-2. This was particularly true for younger children, with nearly 50% of asymptomatic patients under the age of five found to be infected with the virus or bacteria causing the infection.

Higher levels of nasal innate immune activity were found in children with higher levels of respiratory pathogens, whether they were infants or adolescents.

To further investigate the relationship between respiratory infection and nasal innate immunity, Foxman's team compared nasal swabs taken from healthy one-year-old children at both a routine checkup and a follow-up appointment one to two weeks later.

More than half of the children who visited a pediatrician twice tested positive for a respiratory virus, suggesting they had either been infected or cleared in the intervening period. In nearly every case, the child's innate immune activity was higher when they were infected and lower when they were free of the virus.

“This suggests that the nasal antiviral defenses in young children are not always on high alert, but rather become activated in response to infection with a respiratory virus, even when that virus is not causing symptoms,” Foxman says.

The study results indicate that the innate immune system in the nasal passages of children is often overly active, because they are frequently infected with relatively benign germs, such as the rhinovirus responsible for the common cold.

Foxman speculates that young children are more likely to be infected with common seasonal viruses than adults because they have less immune protection from prior infection (such as antibodies). However, because SARS-CoV-2 was a new virus to the human population, neither adults nor children had prior protection when the COVID-19 pandemic began.

In this situation, activation of generalized antiviral immunity in children by other infections may help fight the early stages of SARS-CoV-2 infection, leading to less severe outcomes in children than in adults.

“We have identified respiratory viruses and bacteria as key drivers of enhanced nasal innate immunity in children,” says Foxman. “Our results compel further study on how seasonal respiratory viruses and nasal bacteria influence disease severity of COVID-19 and pediatric immune responses in general.”

more information:
Timothy Watkins et al, High burden of virus and bacterial pathogens impairs nasal innate immunity in children, Journal of Experimental Medicine (2024). DOI: 10.1084/jem.20230911

Provided by Rockefeller University Press

Citation: Study suggests common respiratory infections may protect children from COVID-19 (2024, July 1) Retrieved July 1, 2024 from

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