by Nancy Humphrey

People with food allergies are surprisingly less likely to become infected with SARS-CoV-2, the virus that causes COVID-19, than people without them, a study funded by the National Institutes of Health and co-led by Vanderbilt University Medical Center’s Tina Hartert, MD, MPH, has found.

In addition, the Human Epidemiology and Response to SARS-CoV-2 (HEROS) study published this week in the Journal of Allergy and Clinical Immunology found that a high body mass index (BMI) and obesity raise risk of infection, but asthma does not.

The HEROS study also found that children 12 or younger are just as likely to become infected with the virus as teenagers and adults, but 75% of infections in children are asymptomatic. The study confirmed that SARS-Co-V-2 transmission within households with children is high.

“The finding of a decreased risk of infection among those with food allergy was an unexpected finding,” said Hartert, professor of Medicine and Pediatrics, the Lulu H. Owen Professor of Medicine, director of the Center for Asthma Research and vice president for translational science at VUMC.

“We suspected that those with allergic asthma or allergic rhinitis might have a decreased risk of infection based on data from early in the pandemic, but not food allergy. It’s surprising because there aren’t pathways through which we considered food allergy might decrease infection risk,” she said.

“We surmised that there could be a number of reasons, including behavioral factors that influence exposure, such as those who are food allergic being less likely to eat at restaurants or at gatherings that require removal of mask,” she said. However, the study participants were asked about a list of risk behaviors every two weeks and these did not explain the findings.

Hartert said that it’s also possible that the microbiome or mucosal immunity of those with food allergy protects from infection, or it could be that unmeasured behavioral or other risk factors account for the finding.

“The study was conducted during the early period of the pandemic when there were many questions about whether children were infected or played a major role in community transmission,” Hartert said. “The findings from the HEROS study demonstrated that children were just as likely as adults to be infected, and that they play a critical role as a reservoir of asymptomatic SARS-CoV-2 infection in household and community transmission,” she said, adding that it’s similar to their role in transmission of many respiratory viral pathogens.

The HEROS study monitored more than 4,000 people in nearly 1,400 households including at least one person 21 years or younger in 12 U.S. cities between May 2020 and February 2021. The surveillance took place before the widespread rollout of COVID-19 vaccines in the general population and before the widespread emergence of variants of concern. Participants were recruited from existing NIH-funded studies focusing on allergic diseases. About half of the participating children, teenagers and adults had self-reported food allergy, asthma, eczema or allergic rhinitis.

Hartert, who co-led the study with Max A. Seibold, PhD, director of computational biology and professor of Pediatrics in the Center for Genes, Environment and Health at National Jewish Health in Denver, said the study was a completely remote, direct-to-participant surveillance study that included self-collection of nasal samples and capillary blood samples with no in-person interaction with any research staff. The NIH/National Institute of Allergy and Infectious Diseases (NIAID) sponsored and funded the HEROS study.

Hartert said that the findings that asthma and allergic rhinitis are not risk factors for infection is comforting. “It means that those with asthma and allergic disease are not at any greater risk of becoming infected than those without these diseases. That should be reassuring,” she said.

And Hartert said that while previous research identified obesity as a risk factor for severe COVID-19, the new study identified increasing BMI as associated with increased risk for SARS-CoV-2 infection.

“It’s important not to confuse this with the finding that obesity is associated with severe COVID. Here we are talking about infection risk,” she said.

Hartert said further research is needed on the relationship between food allergy and COVID infection. The researchers are conducting transcriptomic profiling on the serial nasal samples collected before, during and after infection, which they hope will shed light on the findings about food allergy and BMI.

“Replicating the finding and identifying the mechanisms for the decreased risk of infection among those with food allergy could be very interesting in considering strategies to prevent the establishment of infection,” Hartert said.