Because children are “little big vectors” for COVID-19

Offering new insights into the behavior of SARS-CoV-2, a National Institutes of Health (NIH) study suggests that young children and people with obesity may be significant vectors of viral transmission in families.

The NIH’s National Institute of Allergy and Infectious Diseases (NIAID) enlisted scientists from Henry Ford Health and other groups to participate in the project, which focused on the incidence of SARS-CoV-2 infection in families with children and the role of allergic diseases in infection and transmission.

NIAID “wanted to get some answers quickly about COVID in children, homes and families,” study co-author Christine Johnson, PhD, MPH, chair of public health sciences at Henry Ford Health, said in an interview with the AMA.

Henry Ford Health is part of the AMA Health System program, which provides business solutions to equip executives, clinicians, and care teams with the resources they need to lead the future of medicine.

Johnson also directs the Henry Ford Health Center for Allergy, Asthma & Immunology Research, which has been contracted to help collect data for the NIAID study.

She and her team helped monitor 1,394 families from 2020 to 2021, mailing test kits to families and accepting blood and stool samples. Overall, 147 families comprising 261 participants tested positive for COVID-19, says the study, published in the Journal of Allergy and Clinical Immunology.

The objective was to assess the sources of transmission: how it was spreading in families and what role children played in its spread. How much of this was asymptomatic infection?

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Obesity has emerged as a risk factor in acquiring the virus. Age was irrelevant in this association: Anyone who was obese was more likely to become ill than people of normal weight, perhaps because their immune systems weren’t optimized to fight infection.

The findings “definitely showed that the more weight you have on yourself, the more likely you are to become infected … and pass that infection on to someone else in the house,” Johnson said.

This was not the case with asthma. People once assumed that lung disease was a risk factor with COVID-19. The virus attaches itself to angiotensin converting enzyme 2 (ACE2) receptors expressed in the lungs.

In other studies, researchers have found that people with allergic asthma have fewer ACE2 receptors. “Having asthma didn’t make a difference in transmission or getting infected,” Johnson said.

Visit the AMA COVID-19 Resource Center for Physicians to stay up to date on the latest developments.

Although younger children had lower viral loads than adolescents and adults, they were more likely to pass on COVID-19 in their families.

“To me, it validates the notion that kids are great little carriers,” Johnson said. This could be because younger children tend to hug people more, while teenagers tend to keep to themselves, she speculated.

At least 75% of children who have contracted COVID-19 have shown no symptoms. This suggests that they unknowingly had the virus in their nose, but may have spread it to others. Schools ranked first as public sources of exposure compared to health clinics and grocery stores.

Looking back, school closures were likely an effective way to reduce SARS-CoV-2 transmission before the widespread availability of safe and effective vaccines, Johnson said. This is key information that policy makers need to keep in mind when another pandemic hits.

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Doctors predict a tough winter as COVID-19 resurfaces and mixes with influenza and respiratory syncytial virus (RSV).

RSV has stepped up this year and appears earlier, but it wasn’t there in 2021 when people were masking up, Johnson noted. Wearing a mask is an obvious way to avoid infection. This is especially important for people with compromised immune systems, who are expected to mask up at airports and on planes.

As the study findings imply, even patients at high risk for worse outcomes from COVID-19 should avoid close, unmasked contact with young children this winter whenever possible, Johnson said.

— News editor Kevin B. O’Reilly contributed to this report.

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