Wednesday, June 1, 2022
The NIH study found that high BMI and obesity increased the risk of infection, but not asthma.
A study funded by the National Institutes of Health found that people with food allergies were less likely to become infected with SARS-CoV-2, the virus that causes COVID-19, than people without it. In addition, while previous studies have identified obesity as a risk factor for severe COVID-19, a new study identifies 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 SARS-CoV-2 Response Study (HEROS) also found that children 12 years of age or younger were just 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 were published today in Journal of Allergy and Clinical Immunology.
“The results of the HEROS study emphasize the importance of vaccinating children and implementing other public health measures to prevent them from becoming infected with SARS-CoV-2, thus protecting both children and vulnerable members of their household from virus, ”said Anthony C. Fauci, Ph.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH. “In addition, 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 study. NIAID sponsors and funds the HEROS study.
Tina W. Hartert, Ph.D., MPH, co-led the study with Dr. Max A. Seybold. Dr. Hartert is director of the Center for Asthma and Environmental Sciences, vice president of translational science, Lulu H. Owen’s chair of medicine, and professor of medicine and pediatrics at Vanderbilt University School of Medicine in Nashville. Dr. Seybold is Director of Computational Biology, Department of Pharmacogenomics with donations from Wohlberg and Lambert, and Professor of Pediatrics at the Center for Genes, Environment, and Health at National Jewish Health in Denver.
The HEROS research team observed SARS-CoV-2 infection in more than 4,000 people in nearly 1,400 households, including at least one person 21 years of age or younger. This observation took place in 12 cities in the United States between May 2020 and February 2021, before the widespread spread of COVID-19 vaccines among unhealthy workers in the United States and before the widespread emergence of options for concern. Participants were recruited from existing NIH-funded research focused on allergic diseases. Approximately half of the children, teenagers and adults involved had a self-assessment of food allergy, asthma, eczema or allergic rhinitis.
A caregiver in each household took nasal swabs from participants every two weeks to test for SARS-CoV-2 and completed weekly surveys. If a household member develops COVID-19-compliant symptoms, additional nasal swabs were taken. Blood samples are also collected periodically after the family’s first reported illness, if any.
When the HEROS study began, preliminary evidence from other studies showed that the presence of an allergic disease could reduce a person’s susceptibility to SARS-CoV-2 infection. HEROS researchers found that self-assessment of a food allergy diagnosed by a doctor halved the risk of infection, but asthma and other observed 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 a food allergy.
> As all of these conditions were reported on their own, the HEROS research team analyzed the levels of immunoglobulin E (IgE) -specific antibodies, which play a key role in allergic disease, in the blood collected from a subset of participants. According to the researchers, the correspondence between the self-reported food allergy and the measurements of IgE specific to the food allergen supports the accuracy of the self-reported food allergy among HEROS participants, according to the researchers.
Dr. Hartert and colleagues speculate that the type 2 inflammation characteristic of allergic conditions 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 deficiency can limit the virus’s ability to infect them. Differences in risk behavior among people with food allergies, such as less eating out, may also explain the lower risk of infection for this group. However, through two-week estimates, the study team found that households with food allergy participants had only slightly lower levels of exposure in 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 link 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 increases 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 provide evidence of the inflammatory environment associated with the infection, which may change with increasing BMI, according to researchers.
HEROS researchers found that children, teens and adults in the study had about a 14% chance of contracting SARS-CoV-2 during the six-month follow-up period. Infections are asymptomatic in 75% of children, 59% of teenagers and 38% of adults. In 58% of participating households in which one person became infected, SARS-CoV-2 is transmitted to multiple household members.
The amount of SARS-CoV-2 found in nasal swabs, ie the viral load, varied significantly among study participants in all age groups. The range of viral load among infected children is comparable to that of adolescents and adults. Given the incidence of asymptomatic infection in children, a higher proportion of infected children with a high viral load may be asymptomatic compared to infected adults with a high viral load.
HEROS researchers have concluded that young children can be very effective transmitters of SARS-CoV-2 in the household due to their high rate of asymptomatic infection, their potentially high viral load and their close physical interactions with family members.
Further information on the HEROS study is available in this press release from NIAID 2020 and ClinicalTrials.gov under study ID NCT04375761.
NIAID conducts and supports research – in the NIH, in the United States and around the world – to investigate the causes of infectious and immune-mediated diseases and to develop better tools to prevent, diagnose and treat these diseases. News releases, newsletters and other NIAID-related materials are available on the NIAID website.
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MA Seibold et al. Risk factors for SARS-CoV-2 infection and transmission in households with children with asthma and allergies. Prospective observation study. Journal of Allergy and Clinical Immunology DOI: 10.1016 / j.jaci.2022.05.014 (2022).