Wednesday 1 June 2022
The National Institutes of Health study found that a high BMI and obesity increase the risk of infection, but asthma does not.
A study funded by the National Institutes of Health found that people with food allergies are less likely to be infected with SARS-CoV-2, the virus that causes COVID-19, than people without it. In addition, while previous research had identified obesity as a risk factor for severe COVID-19 infection, the new study identified obesity and a high body mass index (BMI) as being associated with an increased risk of SARS-CoV-2 infection. In contrast, the study determined that asthma does not increase the risk of SARS-CoV-2 infection.
The Human Epidemiology and Response to SARS-CoV-2 (HEROS) Study also found that children aged 12 or younger are as likely to contract the virus as adolescents and adults, but 75% of infections in children are asymptomatic. In addition, the study confirmed that transmission of SARS-CoV-2 within families with children is high. These results were published today in Journal of Allergy and Clinical Immunology.
Fauci: “The results of the HEROS study underscore the importance of vaccinating children and implementing other public health measures to prevent them from contracting SARS-CoV-2, thus protecting both children and their at-risk family members from the virus.” D., MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. “Furthermore, the observed association between food allergy and risk of SARS-CoV-2, as well as between BMI and this risk, merits further investigation.” NIAID sponsored and funded the HEROS study.
Hartert, MD, MPH, co-led the research with Max A. Seibold, PhD. Dr. Hartert is director of the Center for Asthma Research and Environmental Sciences, vice president for translational sciences, the Lulu H. Owen Chair of Medicine, and professor of medicine and pediatrics at Vanderbilt University School of Medicine in Nashville. Dr. Siebold is Director of Computational Biology, Wohlberg and Lambert Fellowship Chair for Pharmacogenomics, and Professor of Pediatrics at the Center for Genes, Environment and Health at National Jewish 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 age 21 or younger. This monitoring took place in 12 US cities between May 2020 and February 2021, before COVID-19 vaccines were widely introduced among non-healthcare workers in the United States and before widely worrisome variables emerged. Participants were recruited from current NIH-funded studies focusing on allergic diseases. Nearly half of the participating children, teens and adults had a food allergy, asthma, eczema or allergic rhinitis.
The caregiver in each household took participants’ nose swabs every two weeks to test for SARS-CoV-2 and filled out weekly surveys. If a family member shows symptoms consistent with COVID-19, additional nasal swabs are taken. Blood samples were also collected periodically and after a family’s first illness was reported, if there was one.
When the HEROS study began, preliminary evidence from other research suggested that having allergic diseases might reduce a person’s susceptibility to SARS-CoV-2 infection. The HEROS investigators found that having a self-reported, doctor-diagnosed food allergy cut the risk of infection in half, but asthma and other allergic conditions monitored — eczema and allergic rhinitis — were not associated with a reduced risk. However, participants who reported having a food allergy were allergic to three times as many allergens as participants who did not report having a food allergy.
Since all of these cases were self-reported, the HEROS study team analyzed the levels of immunoglobulin E (IgE), which plays a key role in allergic diseases, in blood collected from a subset of participants. Correspondence between self-reported food allergy and allergen-specific IgE measurements supports the accuracy of self-reported food allergy among HEROS participants, according to the researchers.
Hart and colleagues speculate that type II inflammation, a feature of allergic disease, may reduce 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 risky behaviors among people with food allergies, such as eating out more often, could also explain the lower risk of this group. However, through bi-monthly assessments, the study team found that families with participants with food allergies had only slightly lower levels of community exposure to it than other families.
Previous studies have shown obesity to be a risk factor for severe COVID-19. In the HEROS study, researchers found a strong linear relationship between body mass index – a measure of body fat based on height and weight – and the risk of SARS infection. Each 10-point increase in the percentage of body mass index increases the risk of infection by 9%. Participants who were overweight or obese were 41% more likely to develop an infection than those who were not. More research is needed to explain these results. In this regard, planned analyzes of gene expression in cells collected from participants’ nose swabs before and after infection with SARS-CoV-2 may provide clues about the infection-related inflammatory environment, which may change with increasing body mass index, according to the researchers.
HEROS researchers found that the children, teens, and adults in the study had an approximately 14% chance of contracting SARS-CoV-2 infection during the six-month observation period. Infection was asymptomatic in 75% of children, 59% of adolescents, and 38% of adults. In 58% of participating households where one person was infected, SARS-CoV-2 was transmitted to multiple family members.
The amount of SARS-CoV-2 virus present in nasal swabs, that is, the viral load, varied widely among study participants in all age groups. The range of viral load among infected children was similar to that of adolescents and adults. Given the rate of asymptomatic infection in children, a greater proportion of children with high viral loads may be asymptomatic than adults with high viral loads.
HEROS investigators concluded that young children may be highly effective transmitters of SARS-CoV-2 within the family due to their high rate of asymptomatic infection, potentially high viral loads, and their close physical interactions with family members.
More information about the HEROS study is available in this 2020 NIAID press release and at ClinicalTrials.gov under study ID NCT04375761.
NIAID conducts and supports research — at the National Institutes of Health, throughout the United States, and around the world — to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing, and treating these diseases. Newsletters, fact sheets, and other materials related to NIAID are available on the NIAID website.
About the National Institutes of Health (NIH):
NIH, the country’s medical research agency, includes 27 institutes and centers and is part of the US Department of Health and Human Services. The National Institutes of Health is the primary federal agency that conducts and supports basic, clinical, and polymedical research, investigating the causes, treatments, and treatment of both common and rare diseases. For more information about the National Institutes of Health and its programs, visit www.nih.gov.
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Master Seibold and others. Risk factors for SARS-CoV-2 infection and transmission in families with children with asthma and allergies. A prospective monitoring study. Journal of Allergy and Clinical Immunology DOI: 10.1016/j.jaci.2022.05.014 (2022).