Press release
Wednesday, Jun 1 2022
A NIH study finds that 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 become infected with SARS-CoV-2, a virus that causes COVID-19, than people without them. In addition, while previous studies have identified obesity as a risk factor for severe COVID-19, a new study has identified obesity and high body mass index (BMI) as associated with an increased risk of SARS-CoV-2 infection. In contrast, the study found that asthma did not increase the risk of SARS-CoV-2 infection.
The Human Epidemiology and Response Study on SARS-CoV-2 (HEROS) also found that children 12 years of age and younger are as likely to be infected with the virus as teenagers and adults, but 75% of infections in children are asymptomatic. In addition, the study confirmed that the transmission of SARS-CoV-2 in households with children is high. These findings are published today in Journal of Allergy and Clinical Immunology.
“The findings of the HEROS study emphasize the importance of vaccinating children and implementing other public health measures to prevent SARS-CoV-2 infection, thus protecting both 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 research. NIAID sponsored and funded the HEROS study.
Tina V. Hartert, MD, MPH, co-conducted the research with Mac A. Seiboldom, Ph.D. Dr. Hartert is the director of the Center for Asthma Research and Environmental Science, Vice President of Translational Science, Lulu H. Owen Chair of Medicine, and Professor of Medicine and Pediatrics at Vanderbilt University School of Medicine in Nashville. Dr. Seibold is Director of Computational Biology, Department of Pharmacogenomics with Wolberg and Lambert, and Professor of Pediatrics at the Center for Gene, Environment, and Health at the National Jewish Health Center 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 took place in 12 American cities between May 2020 and February 2021, before the widespread introduction 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 allergic disease studies. Approximately half of the children, teens, and adults who participated had food allergies, asthma, eczema, or allergic rhinitis.
A caregiver in each household took a participant’s nasal swab every two weeks to test for SARS-CoV-2 and complete weekly surveys. If a member of the household develops symptoms that are in accordance with COVID-19, additional nasal swabs are taken. Blood samples were also taken periodically after the family’s first reported illness, if any.
When the HEROS study began, preliminary evidence from other studies suggested that allergic disease may reduce a person’s susceptibility to SARS-CoV-2 infection. HEROS researchers found that self-reported food allergies diagnosed by a doctor halved the risk of infection, but asthma and other accompanying allergic conditions - eczema and allergic rhinitis - 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.
> Since all of these conditions were self-reported, the HEROS research team analyzed levels of antibodies specific for immunoglobulin E (IgE), which play a key role in allergic diseases, in blood collected from a subgroup of participants. According to the researchers, the match between self-reported food allergy and food allergen-specific IgE measurements supports the accuracy of self-reported food allergy among HEROS participants, according to the researchers.
Dr. Hartert and his colleagues speculate that type 2 inflammation, characteristic of allergic conditions, can 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 deficiency could limit the virus’s ability to infect them. Differences in risk behaviors among people with food allergies, such as eating less often in restaurants, may also explain the lower risk of infection for this group. However, through two-week assessments, the study team found that households with food-allergic participants had only slightly lower levels of community exposure 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 link between BMI, a measure of body fat based on height and weight, and the risk of SARS-CoV-2 infection. Each increase in body mass index of 10 points increased the risk of infection by 9%. Participants who were overweight or obese had a 41% higher risk of infection than those who were 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 indicate an inflammatory environment associated with the infection, which may change as BMI increases, according to researchers.
HEROS researchers found that children, teenagers and adults in the study had about a 14% chance of SARS-CoV-2 infection during the six-month follow-up period. Infections were asymptomatic in 75% of children, 59% of adolescents, and 38% of adults. In 58 percent of households where one person became infected, SARS-CoV-2 was transmitted to multiple household members.
The amount of SARS-CoV-2 found in nasal swabs, ie viral load, varied greatly among study participants in all age groups. The extent of viral load among infected children was comparable to that of adolescents and adults. Given the rate of asymptomatic infection in children, a higher percentage of infected children with a high viral load may be asymptomatic compared to infected adults with a high viral load.
HEROS researchers concluded that young children can be very effective carriers of SARS-CoV-2 in the household due to their high rate of asymptomatic infection, potentially high viral load and close physical interactions with family members.
Additional information on the HEROS study is available in this NIAID 2020 press release and on ClinicalTrials.gov under study identifier NCT04375761.
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References
MA Seibold et al. Risk factors for SARS-CoV-2 infection and transmission in households with children with asthma and allergies. Prospective surveillance study. Journal of Allergy and Clinical Immunology DOI: 10.1016 / j.jaci.2022.05.014 (2022).