Good news for people with food allergies — having a food allergy cuts your risk of being infected with COVID-19 by half, according to the results of the Human Epidemiology and Response to SARS-CoV-2 (HEROS) study, a National Institute of Health-funded study. The study provides strong evidence that people with asthma, eczema, and upper respiratory allergy (hay fever and allergic rhinitis) were not at increased risk for SARS-CoV-2 infection. The findings were published in the Journal of Allergy and Clinical Immunology.1

The study also confirmed that obesity (BMI >30) is a risk factor for SARS-CoV-2 infection, not just for severe COVID-19 symptoms. The authors reported that “every 10-point increase in BMI percentile raised the risk of infection by 9%. Participants who were overweight or obese had a 41% greater risk of infection than those who were not,” the researchers said.

The researchers speculated that inflammation caused by type 2 cytokines, which are common with food allergies, may drive the decreased risk for COVID-19 infection found among people with food allergies. Previous work by Max A. Seibold, PhD, lead author of the study, found that allergic type 2 inflammation can reduce airway levels of the SARS-CoV-2 receptor gene ACE2, suggesting that patients with food allergies may have lower ACE2 receptor levels, reducing the ability of the virus to infect cells in these individuals.2 Dr Seilbold is director of computational biology, the Wohlberg and Lambert Endowed Chair of Pharmacogenomics, and a professor of pediatrics in the Center for Genes, Environment, and Health at National Jewish Health in Denver.  


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 “Our findings that diseases characterized by different types of inflammation are associated with infection risk, suggest underlying inflammation is an important determinant of susceptibility to SARS-CoV-2 infection,” said study senior author Tina V. Hartert, MD, MPH, who is director of the Center for Asthma and Environmental Sciences Research at Vanderbilt University School of Medicine in Nashville.2 

About the HEROS Study

To study whether patients with asthma and other allergic conditions are more susceptible to COVID-19 infection, the HEROS study team monitored COVID-19 infections in more than 4000 people in nearly 1400 households that included at least 1 person aged 21 years or younger in 12 US cities between May 2020 and February 2021, before the widespread rollout of COVID-19 vaccines and before the widespread emergence of the Delta and Omicron variants. Participants were recruited from existing, NIH-funded studies focused on allergic diseases. Roughly half of the participating children, teenagers, and adults had self-reported food allergy, asthma, eczema, or allergic rhinitis. 

A caregiver in each household took nasal swabs of participants every 2 weeks to test for SARS-CoV-2 and filled out weekly surveys. If a member of the household developed symptoms consistent with COVID-19, additional nasal swabs were taken. Blood samples also were collected periodically and after a family’s first reported illness, if there was one.

One or more atopic conditions, excluding asthma, were self-reported by 52% and 57% of caregivers and children/teenagers, respectively. These included food allergy, eczema, and upper respiratory allergy (Table).

Table. Self-Reported Atopic Conditions

AllergyCaregiver, %Children/Teenagers, %
Food allergy10.220.7
Eczema10.224.0
Hay fever or allergic rhinitis4744.5

The HEROS investigators found that having self-reported, physician-diagnosed food allergy cut the risk of infection in half (adjusted hazard ratio, 0.50), but asthma and the other allergic conditions monitored—eczema and allergic rhinitis—were not associated with reduced infection risk. However, the participants who reported having food allergies were allergic to 3 times as many allergens as the participants who did not report having food allergies.

Because all these conditions were self-reported, the HEROS study team analyzed the levels of immunoglobulin E (IgE)-specific antibodies in blood collected from a subset of participants. They found concordance between self-report and food allergen IgE measurement, which supports the accuracy of self-reported food allergy among HEROS participants, according to the investigators.   

Differences in risk behaviors among people with food allergies, such as eating out at restaurants less often, also could explain the lower infection risk for this group. However, through biweekly assessments, the study team found that households with food-allergic participants had only slightly lower levels of community exposure than other households.

Other key findings of the HEROS study included:

  • Confirmation that obesity and high BMI are risk factors for SARS-CoV-2 infection, not just for severe COVID-19 disease. Every 10-point increase in BMI percentile raised the risk of infection by 9%. Participants who were overweight or obese had a 41% greater risk of infection than those with a normal weight.
  • The probability of SARS-CoV-2 infection was similar (14%) among children 12 years of age and younger, teenagers, and adults. Infections were asymptomatic in 75% of children, 59% of teenagers, and 38% of adults.
  • SARS-CoV-2 transmission within households with children is high, approximately 58%. Given the rate of asymptomatic infection in children, a larger proportion of infected children with high viral loads may be asymptomatic compared with infected adults with high viral loads. 

The HEROS investigators concluded that “young children may be very efficient SARS-CoV-2 transmitters within the household due to their high rate of asymptomatic infection, their potentially high viral loads, and their close physical interactions with family members.” 

“The HEROS study findings underscore 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 the virus,” said Anthony S. Fauci, MD, director of the National Institute of Allergy, and Infectious Diseases (NIAID), in a news release.3 “Furthermore, the observed association between food allergy and the risk of infection with SARS-CoV-2, as well as between body-mass index and this risk, merit further investigation.” NIAID sponsored and funded the HEROS study.3

Further information about the HEROS study is available in this 2020 NIAID press release and at ClinicalTrials.gov under study identifier NCT04375761

References 

1. Seibold MA, Moore CM, Everman JL, et al. Risk factors for SARS-CoV-2 infection and transmission in households with asthmatic and allergic children. A prospective surveillance studyJ Allergy Clin Immunol. 2022;S0091-6749(22)00752-7. [Published online ahead of print] doi:10.1016/j.jaci.2022.05.014

2. Study finds food allergy is associated with lower risk of SARS-CoV-2 infection. National Jewish Health. News release. June 1, 2022. Accessed June 9, 2022. https://www.nationaljewish.org/about/news/press-releases/2022-news/study-finds-food-allergy-associated-with-lower-risk-of-sars-cov-2-infection

3. Food allergy is associated with lower risk of SARS-CoV-2 infection. National Institute of Allergy and Infectious Diseases. News release. June 1, 2022. Accessed June 9, 2022. https://www.eurekalert.org/news-releases/954460