A study funded by the National Institutes of Health (NIH) found that people with food allergies are less likely to become infected with SARS-CoV-2, the virus that causes COVID-19, than people without them. In addition, while previous research identified obesity as a risk factor for severe COVID-19, the new study has identified obesity and high body mass index (BMI) as associated with a increased risk of SARS-CoV-2 infection. In contrast, the study found that asthma does not increase the risk of SARS-CoV-2 infection.
The study of human epidemiology and the response to SARS-CoV-2 (HEROS) also found that children 12 years of age and younger were more likely to become infected with the virus than adolescents and adults. 75% of infections in children are asymptomatic. In addition, the study confirmed that the transmission of SARS-CoV-2 to households with children is high. These findings were published [June 1] in the Journal of Allergy and Clinical Immunology.
“The results of the HEROS study underscore the importance of vaccinating children and implementing other public health measures to prevent them from becoming infected with SARS-CoV-2, thus protecting children and vulnerable members of their household from the virus.” , said Anthony S. Fauci. , MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH. “Furthermore, the observed association between food allergy and the risk of SARS-CoV-2 infection, as well as between body mass index and this risk, deserves further investigation.”
NIAID sponsored and funded the HEROS study.
Tina V. Hartert, MD, MPH, led the research with Max A. Seibold, PhD. Dr. Hartert is director of the Center for Environmental and Asthma Research, vice president of translational science, chair Lulu H. Owen, and professor of medicine and pediatrics at Vanderbilt University School of Medicine in Nashville. Dr. Seibold is director of computational biology, Wohlberg and Lambert Endowed Chair of Pharmacogemics, and professor of pediatrics at the National Jewish Health Center for Health, Environment, and Health in Denver.
The HEROS study team monitored SARS-CoV-2 infection in more than 4,000 people in nearly 1,400 households that included at least one person 21 years of age or younger. This surveillance was conducted in 12 U.S. cities between May 2020 and February 2021, before the widespread deployment of COVID-19 vaccines among non-health workers in the United States and before the widespread emergence of variants. of concern. Participants were recruited from existing NIH-funded studies focused on allergic diseases. About half of the participating children, teens, and adults had a food allergy, asthma, eczema, or allergic rhinitis.
One caregiver from each household took participants ’nasal swabs every two weeks to test for SARS-CoV-2 and filled out weekly surveys. If a household member had symptoms compatible with COVID-19, additional nasal swabs were taken. Blood samples were also collected periodically and after the first reported illness of a family, if any.
When the HEROS study began, preliminary evidence from other research suggested that having an allergic disease could reduce a person’s susceptibility to SARS-CoV-2 infection. HERO researchers found that having a self-reported and allergy-diagnosed food allergy halved the risk of infection by half, but asthma and other controlled allergic conditions (eczema and allergic rhinitis) they were not associated with a reduced risk of infection. However, participants who reported having a food allergy were allergic to three times more allergens than participants who did not report having a food allergy.
Because all of these conditions were self-reported, the HEROS study team analyzed the levels of specific antibodies to immunoglobulin E (IgE), which play a key role in allergic disease, in the blood collected from a subset of participants. According to the researchers, a correspondence between self-reported food allergy and food allergen-specific IgE measures supports the accuracy of self-reported food allergy among HERO participants.
Dr. Hartert and colleagues speculate that type 2 inflammation, a feature of allergic conditions, can lower the levels of a protein called the ACE2 receptor on the surface of airway cells. SARS-CoV-2 uses this receptor to enter cells, so its scarcity could limit the virus’s ability to infect them. Differences in risk behaviors among people with food allergies, such as eating out in restaurants less frequently, could also explain the lower risk of infection for this group. However, through fortnightly assessments, the study team found that households with participants allergic to food only had slightly lower levels of exposure to the community than other households.
Previous studies have shown that obesity is a risk factor for severe COVID-19. In the HEROS study, researchers found a strong, linear relationship between BMI, a measure of body fat based on height and weight, and the risk of SARS-CoV-2 infection. Each 10-point increase in BMI percentile increased the risk of infection by 9%. Overweight or obese participants had a 41% higher risk of infection than those who did not.
More research is needed to explain these findings. In this regard, planned analyzes of gene expression in cells collected from participants’ nasal swabs before and after SARS-CoV-2 infection may provide clues about the inflammatory environment associated with the infection. which may change as the BMI rises, according to the researchers.
HERO researchers found that children, adolescents, and adults in the study had about a 14% chance of SARS-CoV-2 infection during the six-month surveillance period. Infections were asymptomatic in 75% of children, 59% of adolescents, and 38% of adults. In 58% of participating households where a person became infected, SARS-CoV-2 was transmitted to several members of the household.
The amount of SARS-CoV-2 found in nasal swabs, that is, viral load, varied widely among study participants across all age groups. The range of viral load among infected children was comparable to that of adolescents and adults. Given the rate of asymptomatic infection in children, a higher proportion of children infected with high viral loads may be asymptomatic compared to adults infected with high viral loads.
HERO researchers concluded that young children may be highly efficient transmitters of SARS-CoV-2 at home due to their high asymptomatic infection rate, potentially high viral loads, and close physical interactions with family members.
More information about the HEROS study is available in this 2020 NIAID press release and at ClinicalTrials.gov with study ID NCT04375761.
This press release was originally published by the National Institutes of Health on June 1, 2022.